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An Assessment of Exotic Plant Species of Rocky Mountain National Park

Summary Information for Remaining Exotic Plant Species


Agropyron cristatum (L.) Gaerin.
Crested wheatgrass (Poaceae)

Known locations in RMNP: Introduced as part of seed mixes along road shoulders, mostly near Park Headquarters.
Assessment: Not believed to be spreading in Park. An intermediate number of patchy populations. When all populations are added together, estimated to cover a total area less than 5 hectares. Found in areas disturbed within the last 50 years, and may be retarding succession.
Origin: Russia. Introduced grass from Europe and Asia.
Geographic Range: Cultivated in North Dakota, South Dakota, Wyoming, and Colorado from 5000 to 8500'.
Ecological Range: On open hillsides and on salt desert shrub, sagebrush, pinyon juniper, mountain brush and ponderosa pine communities. Found in areas of 5-14" annual precipitation, has a generally low moisture requirement.
Soils: Adapted to loamy, clay soils. Less adapted to heavy clays and sand. Most abundant on dry, medium textured soils.
Reproduction: Perennial, reproduces by seeds. Starts growth in early spring and seeds reach maturity in early summer.
Seed longevity: Studies report seeds remain viable for at least 2 years, and up to 12 years in soils.
Seed production: A highly productive seed producer under a wide range of conditions.
Germination: Optimum germination occurs between 15-25 C.
Response to shading: Light is not a requirement for crested wheatgrass germination.
Competition: Fairly shade, drought, and cold tolerant. A very long lived plant.
Notes: Commonly planted for soil stabilization.
References:

Dillman, A.C. 1946. The beginnings of crested wheatgrass in North America. Journal 
    of American Society Agronomy 38:237-250.

Harris, G.A. 1967. Some competitive relationships between Agropyron spicatum and 
    Bromus tectorum. Ecological Monographs. 37:89-11 1.

Johnson, K.L. 1983. Crested wheatgrass: It's values, problems, and myths. Symposium 
    Proceedings, Utah State University. Logan Utah.

Agropyron intermedium (Elytrigia intermedia, Thinopyrum intermedium)
Intermediate wheatgrass (Poaceae)

Assessment: An intermediate number of patchy distributed populations. When added together, all populations would cover an area less than 5 hectares. Found in mid-succession sites disturbed in the last 10-50 years. Presence of intermediate wheatgrass may delay establishment of native species.
Origin: Introduced from Europe for pasture, hay, range seedlings, and erosion control.
Ecological distribution: Dry to mesic sites, chiefly along roadsides, and in other waste places. In sagebrush, mountain brush, pinyon juniper, aspen, ponderosa pine, and spruce fir communities. Adapted to well-drained soils where the mean annual ppt. is 30-36 cm or more. It is only slightly inferior to Agropyron cristatum in persistence, drought tolerance, and winter hardiness.
Reproduction: Perennial, reproduces by rhizomes and seeds. Rhizomes are moderately vigorous.
Other: The grass is highly palatable to all animals in the spring and summer. Commonly planted to revegetate range.
Control: Intermediate wheatgrass is relatively easy to eradicate, and is susceptible to cutting in shooting stage and close grazing.


Agrostis stolonifera L. (Agrostis gigantea Roth, Agrostis alba L.)
Redtop (Poaceae)

Known locations in RMNP: Introduced in hay meadows, and is well established. Found in Lower Black Canyon and Horseshoe Park alluvial fan.
Assessment: An intermediate number of patchy populations. When all populations are added together, would cover an area of 5-10 hectares. Found in late succession sites disturbed in the last 11-50 years.
Origin: Likely originated from Eurasia, introduced as a lawn and pasture grass.
Geographic Range: Present in cooler parts of U.S., widely distributed in Colorado from 3500-9000'.
Ecological Range: Along waterways, often partially or totally submersed in shallow running water. In marshes, wet meadows, and near seeps in greasewood, pinyon juniper, aspen, and spruce fir communities. Establishes in hay meadows, ditches, cultivated pastures. Adapted to a wide range of soil and climatic conditions.
Soils: Grows on acid soils, poor clayey soils of low fertility, and poorly drained land. Moderately salt tolerant.
Reproduction: Reproduces by seeds and creeping rhizomes, sometimes mat forming. Starts growth in early spring, flowers in early summer and seeds mature by August.
Other: A fair forage for elk. Can withstand flooding for extended periods.


Alopecuris pratensis L.
Meadow foxtail grass (Poaceae)

Locations in RMNP: Used for erosion control and seeding along highways.
Assessment: A few scattered populations in park. When all populations are added together, would cover an area less than 5 hectares. Plants believed to be having little effect on natural processes.
Origin: Introduced from Europe, often used for range rehabilitation and erosion control.
Geographic distribution: Common in eastern states, found throughout northern U.S. and Alaska.
Ecological distribution: Well adapted to wet meadows. Mesic to wet sites along roads, in pastures, meadows, and aspen conifer communities.
Reproduction: Perennial, reproduces by seeds and occasionally with short rhizomes. Plants can be difficult to establish because of weak, slow-growing seedlings.


Alyssum alyssoides (L.) L.
Yellow alyssum, pale alyssum (Brassicaceae)

Known locations in RMNP: Documented in Hollowell Park, Moraine Park picnic area, Deer Mountain. Common on dry pine forests.
Origin: Introduced from Europe.
Geographic distribution: Widespread in North America. Found in Colorado from 4500-7000'.
Ecological distribution: Bunchgrass, sagebrush, pinyon juniper, and mountain brush communities. Waste areas, foothills, croplands and fields. Often on woody slopes.
Soils: Common on dry, gravely soil, silty clay soils optimal.
Reproduction: Annual forb, reproduces by seeds. Mature seeds dispersed from mid-June to mid-July.


Amaranthus retroflexus L.
Redroot pigweed (Amaranthaceae)

Locations in RMNP: Moraine Park, found in disturbed sites at low elevations.
Origin: Introduced from tropical America. Some sources believe it to be a native riverbank pioneer of central and eastern U.S.
Geographic Range: General throughout U.S. and Canada, in Colorado up to 8500'. Rare on the highly acidic soils of the southeastern U. S.
Ecological Range: Cultivated fields, yards, fence rows and waste grounds, one of the commonest weeds of gardens. Found in open, disturbed sites where annual weeds pre-dominate.
Soils: Coarse textured soils that are moist are best for germination. Found on a variety of soil types from sandy loam to clay. Often associated with rich soils.
Reproduction: Annual, reproduces by seeds, a warm season weed. As a result of rapid germination and reduced seed dormancy, may be have two generations per year. Does not reproduce vegetatively. Flowers July to September, seeds germinate throughout summer months with adequate moisture.
Seed production: 117,400 seeds/plant.
Seed longevity: Seeds remain viable up to 6 years in soil.
Seed dispersal: Seeds can be dispersed by water, by wind, by animals after ingestion, and as contaminants of crop seeds or machinery.
Germination: Occurs any time during growing season when soil moisture is sufficient. Germinate in warmer months only (optimal temp. 30-40 C). Germination is prevented by light unless seed coat is removed.
Competition: Seldom found in closed or shaded communities. However, A. retroflexus has been observed to reduce the yield of a variety of crops by competition. A. retroflexus may be a poor competitor in soils with a pH below 6.0.
Level of Impact: High potential rate of increase, when 1000 seeds were sown on separate plots of 25m2, produced an average of 140 plants and a yield of 266,400 seeds/plot.
Control: Relatively susceptible to most herbicides recommended for control of broad-leaf weeds.
Mechanical: During the first 4 weeks of growth, seedlings grow fairly slowly if temperatures are cool, and are susceptible to cultivation. Older plants are often able to recover from clipping, trampling or other injury
Cultural: 2,4-D may also reduce seed yield, applied at rates of 0.56 and 1.2 kg/ha.
Notes: Sometimes accumulates excess nitrates causing cattle to bloat. Redroot pigweed provides food and cover for upland game birds, the seeds were harvested by Native Americans and ground into flour.
References:

Chu, C. P.M. Ludford, J.L. Ozbun, and R.D. Sweet. 1978. Effects of temperature 
    and competition on the establishment and growth of redroot pigweed and common 
    lambsquarters. Crop Science 18:308-310.

Rojas-Garciduenas, M. and T. Komedahl. 1960. The effect of 2,4-D on germination 
    of pigweed seed. Weeds 8: 1-5.

Weaver, S.E. and E.L. McWilliams. 1980. The biology of Canadian Weeds. 44. 
    Amaranthus retroflexus L., A. powellii S.Wats, and A. hybridus L. Canadian 
    Journal of Plant Science. 60: 1215-1234.

Ambrosia tomentosa Nutt. (A. Nels.) (Franseria discolor)
Skeleton leaf bursage, bur ragweed, silverleaf (Asteraceae)

Known Locations in RMNP: Moraine Park, near east parking lot.
Assessment: Currently believed to have patchy distribution in Park. When all populations added together, would cover an estimated area less than 5 hectares. Currently believed to be having low levels of impact on natural processes.
Origin: Most sources list as a native plant, common to plains region.
Geographic distribution: Western Great Plains and Rocky Mountain states. Colorado from 5000 to 8000'.
Ecological distribution: Expected wherever land is cultivated. Meadows, stream banks, waste places, pastures and poorly irrigated fields, dry regions of the plains.
Soil: Survives well under a variety of soil moisture conditions.
Reproduction: Perennial, reproduces by seeds and creeping roots. Flowers July to September.
Competition: An aggressive weed in western Nebraska.
Level of Impact: Although a native plant of the plains region, is designated as noxious in some states.
Control: A difficult weed to eradicate because of its extensive horizontal root system.


Arabis glabra L. Berah
Tower mustard, rockcress (Brassicaceae)

Origin: Native of North America.
Assessment: A few scattered populations are found in RMNP. When added together, all populations would cover an area less than 5 hectares. Found mostly on sites disturbed in last 10 years, and appears to be having little effect on natural processes.
Reproduction: Biennial forb, reproduces by seeds.


Asparagus officinals L.
Asparagus (Asparagaceae)

Origin: Mediterranean region, introduced from Eurasia.
Known locations in RMNP: Moraine Park, found at a few sites near old cabins and open grassy areas.
Assessment: Not believed to be problem. Only few scattered populations found around old homesteads.
Ecological distribution: Cultivated food plant, escaping and establishing along canal banks, in orchards, and among indigenous riparian vegetation.
Ecological distribution: Escaped from cultivation, found in irrigated ditches and roadsides.
Reproduction: Perennial forb.


Barbarea vulgaris R. Br.
Bitter wintercress, yellow rocket (Brassicaceae - Cruciferae)

Origin: Introduced from Eurasia; likely of Mediterranean origin.
Known locations in RMNP: Reported in Left Hand Canyon in Boulder, not known to occur in park.
Assessment: Currently not a threat to park. Plant is generally associated with disturbance and may eventually reach park area. In this case, it may be useful to control small stands so that additional seeds are not produced (see Control section).
Geographic distribution: Abundant in northeastern and north-central states, also Pacific Northwest.
Ecological distribution: Riparian or other moist communities. Gardens, clover and alfalfa fields, small grain fields, pastures, stream banks, moist woods, waste places, and roadsides. Common in recently disturbed areas and is considered an early succession species.
Soils: Generally no specific substrate requirements. Especially on rich, alluvial soils. Can tolerate dry to sub hydric soils. Grows on sand, silts, clays of varying fertility and pH.
Reproduction: Perennial or generally biennial, reproduces by seeds. Flowers April to June.
Seed longevity: Seeds can remain dormant for 10-20 years in soil.
Seed production: 38,000 seeds/plant (average for large sized plant).
Seed dispersal: Most seeds are deposited within one meter of parent. Seeds are coated with adhesive mucus which can promote attachment to animals. Remain viable after passing through the digestive tracts of cattle, horses, and pigs.
Germination: Requires vernalization, with several weeks at 5 C or less. Dormancy is induced by drying or cool periods of less than 10 C.
Response to shade: Can grow in open (bare ground) to woodland (with complete canopy cover).
Competition: Known to reduce crop yields as a result of relatively rapid increase in numbers, low plant edibility at maturity, and long seed dormancy. Commonly invades grass legume meadows in New York state. However, is generally classified as an opportunist that is found in recently disturbed areas. Observed to have high mortality in mesic soils dominated by species such as Agropyron repens and Poa prarensis.
Level of impact: Listed as noxious in many states.
Control: Clipping after seed has been produced is not recommended because seeds will mature and remain viable on cut stalks.
Mechanical: Pull or hand hoe scattered plants just as they begin to blossom. Rosettes and root systems that are clipped or mowed are capable of regeneration. However, the Ontario Weed Commission recommends mowing (low enough to catch the lowest flower-stalks) rather than herbicide application when the plants are flowering to limit seed production.
Chemical: The Ontario Weed Committee recommends 2,4-D (LV ester) at 0.84 to 1.1 kg/ha applied in September or October, or in early May before flowering of B. vulgaris. Shows resistance to MCPA.
References:

Lindsay, D.R. and I.J. Bassett. 1951. Preliminary report on the life history of 
    yellow rocket (Barbarea vulgaris R. Br.) Proceedings of National Weed 
    Committee Canada, East Sec. 5:73-75.

MacDonald, M.A. and P.B. Cavers. 1991. The biology of Canadian Weeds. 97. Barbarea 
    vulgaris R. Br. Canadian Journal of Plant Science. 71: 149-166.

Berteroa incana (L.) DC. (Alyssum incanum L.)
Hoary alyssum (Brassicaceae)

Known locations in RMNP: Embankment of Highway 34 bypass, 1/3 mile east of Estes Park city limits. Very abundant weed just outside of park, assumed to be in park, but not confirmed.
Origin: Introduced from Europe.
Geographic distribution: Locally common in northeastern states and infrequent in central states.
Ecological distribution: Meadows, pastures, and waste areas, forms dense stands along roadsides. Hoary alyssum is most abundant in recently disturbed sites such as roadsides. Soils: Mostly on dry sandy or gravely soils.
Reproduction: Annual (sometimes biennial), reproduces by seeds. Flowers from June to September, emerges early spring, grows throughout frost-free periods.
Seed production: Each pod contains 7-12 seeds.
Level of impact: Listed as noxious in some states.
Control: Pull or hand hoe plants.


Bromus japonicus Thunb. ex Murr. (Bromus patulus)
Japanese brome, Japanese or Meadow chess (Poaceae)

Known locations in RMNP: SE slope of Deer Mountain, possibly introduced as contaminant of seed mixes.
Origin: Eurasia.
Geographic distribution: Throughout all of U.S. except northern Maine and southern Florida. Found in eastern half of Colorado from 4000 to 7500'.
Ecological distribution: In mostly disturbed sites, greasewood, sagebrush, mountain brush, and juniper communities, and open slopes. A nuisance in depleted ranges, hayfields, and dry soils in waste or disturbed areas.
Reproduction: Winter annual, cool season grass, reproduces by seeds. Matures May-August. Young plants overwinter and reach maturity in early spring.
Control: Japanese brome is similar to cheatgrass in its ecology, life cycle, and response to control measures.
Mechanical: Mow before seed heads are formed to prevent seed production.
Other: Consecutive annual burns may reduce brome density and standing crop.
References:

Whisenant, S.G. and D.W Uresk. 1990. Spring burning of Japanese brome in a western 
    wheatgrass community. Journal of Range Management 43:205-208.

Camelina microcarpa Andrz. ex DC.
Smallseed falseflax, falseflax (Brassicaceae - Cruciferae)

Known location in RMNP: Moraine Park to Fern Lake, East Portal. Suspected to be brought into the park from hay fed to livestock.
Origin: Introduced from Europe.
Geographic distribution: Throughout all of U.S. except mid-Atlantic Coast states and states on the southern U.S. boundary. Widely scattered over Colorado from 3500-7500'.
Ecological distribution: Roadsides, foothills, gardens, and other disturbed moist to dry sites. Disturbed areas such as fields, waste places, and roadsides, mostly growing in flax areas.
Soils: A common weed of disturbed soils.
Reproduction: Annual (or winter annual), reproduces by seeds. Flowers April to September.
Germination: Majority of seeds germinate in early spring.
Control (mechanical): Mow close to surface to prevent seed production.
Chemical: 2,4-D has been used in pastures and small grain crops to control C. microcarpa. 2,4-D should be applied early in spring before seeds are formed.


Capsella bursa-pastoris (L.) Medic.
Common shepherd's purse (Brassicaceae)

Known locations in RMNP: Prospect Mountain, Hidden Valley Ranch. A common adventive weed of disturbed soils, montane.
Assessment: Few scattered populations. When all populations are added together, would cover an estimated total area less than 5 hectares. Having small overall impact, may inhibit the establishment of native species.
Origin: Introduced from southern Europe.
Geographical distribution: A cosmopolitan weed, widespread throughout North America. Common in Colorado up to 9000'.
Ecological distribution: Common in croplands, gardens, lawns, and non-cultivated areas. Small grain fields, gardens, lawns, hay fields, and waste areas.
Soils: Optimal soil pH ranges from 7.1 to 8.5.
Reproduction: Annual or winter annual herb (sometimes biennial), reproduces by seeds. A self-fertile species. Flowering may occur from April to December, often one of the first flowers in the spring.
Seed production: A single plant may produce 2000 seeds or more a year, two or three generations in a year are not infrequent. According to some sources, may produce 3O,000- 4O,000 seeds/plant.
Seed longevity: Seeds long-lived in soils, remain viable in soil up to 5 years. Seeds capable of withstanding large amounts of pressure, preventing germination. Seeds may remain dormant as long as 35 years.
Seed dispersal: Medium potential for dispersal based on seed size and seed shape. Seeds remain viable after passing through digestive tracts of birds, cattle and horses.
Germination: Seeds show a dormancy, which is removed by a period of cold treatment (one winter period is sufficient for most seeds). Low temperatures (below 15 C) aid in breaking seed dormancy. Peak germination occurs in late spring or early summer. Darkness suppresses seed germination.
Control: Long lived seeds, coupled with high seed production makes this plant a persistent weed. Notes: Plant capable of surviving low temperatures (down to -10 to -15 F).


Carum carvi L.
Wild caraway (Apiaceae-Umbelliferae)

Origin: Europe. escaped from cultivation.
Known locations in RMNP: unknown.
Geographic distribution: Widespread throughout U.S., common in northeastern U.S. Found in western half of Colorado, except in the extreme western part of the state from 5000-9500'.
Ecological distribution: A cultivated plant, the fruits used for flowering. Escaping and establishing in mountain meadows, hay fields, along irrigation ditches and mountain townsites.
Reproduction: Biennial, occasional perennial, reproduces by seeds. Flowers June and July.
Competition: Invades mountain meadows.
Control: Mow or pull plants before seeds are formed.


Cerastium vulgatum L. (Cerastium fontanum)
Mouseear chickweed (Caryophyllaceae)

Known locations in RMNP: Mouth of Red Gulch, Horseshoe Park alluvial fan, Hidden Valley Creek Beaver ponds.
Origin: Introduced from Eurasia.
Geographic distribution: Throughout most of U.S. and southern Canada. In north-central, central, and south central Colorado from 3500 to 10,000'.
Ecological distribution: Lawns, open sites, and often riparian habitats. Weeds, lawns, pastures, abandoned cultivated fields, meadows, roadsides, and streambanks. Often a troublesome weed, especially a problem in areas that are excessively watered or shaded.
Reproduction: Biennial or short lived perennial, reproduces by seeds with occasional development from creeping roots. Flowers April to October.
Seed production: A normal sized plant will produce 6500 seeds.
Seed longevity: Seeds are long lived, and may remain viable in soil for several years, and possibly up to 40 years.
Seed dispersal: Due to low weight of seeds, seeds are effectively dispersed by wind.
Level of impact: A troublesome weed that is difficult to control.
Control: Chickweed has been controlled in turf areas by good management techniques.
Chemical: A mixture of 2,4-D, mecocarp, and dicamba applied in spring has been used to control this plant in grassy waste areas.


Chenopodium album L.
Lambsquarters, white goosefoot, pigweed (Chenopodiaceae)

Known locations in RMNP: Documented in montane uplands by Denver Botanical Gardens.
Assessment: When added together, all populations would cover an area less than 5 hectares. Plants found mainly in areas disturbed in the last 5 years, and seem to be having little or no effects on natural processes.
Origin: Introduced and naturalized from Eurasia, a native of Asia. A common crop seed contaminant.
Geographic distribution: Widespread throughout U.S. and Colorado.
Ecological distribution: A colonizing species that can be found in disturbed habitats. Cultivated crops, gardens, grain fields, and waste grounds, vacant lots, other disturbed soils. Can be found in most habitats of the world, except in desert regions. Not commonly found in natural situations such as native woodland and prairie.
Soils: Typically associated with nitrogen rich soils. Does best on fertile heavy soils, but can be found in all soil types and over a wide range of pH values.
Reproduction: Annual forb. reproduces by seeds. Flowers from June to September.
Seed production: An average plant will produce about 3000 seeds, large plants may produce 500,000 seeds.
Seed longevity: Seeds very long lived, may remain viable for over 30 40 years.
Seed dispersal: Low-medium potential for dispersal based on seed size and seed weight. Lacks any specialized seed dispersal mechanism so most seeds are deposited near plant. Seeds are not buoyant, but may be washed into ditches and can be moved long distances. Seeds remain viable after passing through digestive tract of birds such as sparrows, pigs, and cows.
Germination: Seeds germinate in early spring when nitrate is available. Light has also been reported as necessary for germination. Germination is inhibited in areas shaded by green plants. Seeds remain viable under either prolonged moisture or dryness, but will rapidly germinate under optimal conditions.
Competition: Succulent, fast growing herb which rapidly removes moisture from the soil. Very competitive weed because of its high water use and rapid growth. Competes strongly with corn for nitrogen, potassium, calcium, and magnesium. However, it is not a highly aggressive, destructive plant.
Control: Susceptible to commonly recommended herbicidal foliage sprays. However, any postmergance herbicide must be applied while plant is young because plants rapidly become woody and resistant.
Chemical: Sensitive to MCPA salt, 2,4 -D amine and MCPB salt, and many other chemicals. Highly susceptible to MCPA regardless of the application time during the day. Cylocate has also been used for control. Mechanical: C. album is unable to withstand clipping.
References

Bassett, A. and C.W. Compton. 1978. The biology of Canadian weeds. 32. Chenopodium 
    album L. Canadian Journal of Plant Science 58:1061-1072.

Cumming, B.G. 1963. The dependence of germination on photoperiod, light quality, 
    and temperature in Chenopodium ssp. Canadian Journal of Botany 41: 1211 - 1233.

Weaver, M.L. and R.E. Nylund 1965. The susceptibility of annual weeds and Canada 
    thistle to MCPA applied at different times of day. Weeds 13:110-113.

Chenopodium capitatum L.
Strawberry blite, Blite mulberry

Known locations in RMNP: Documented in montane uplands by Denver Botanic Gardens.
Origin: Native to North America and to Europe.
Geographic distribution: Mostly in northeastern states and Rocky Mountain states.
Ecological distribution: Cultivated ground, waste areas and especially in new clearings in woodland regions.
Reproduction: Annual, reproduces by seeds. Flowers from July to September.
Control: Hand hoe in early season to prevent seed production.


Chenopodium glaucum L.
Oak- leafed goosefoot (Chenopodiaceae)

Origin: Introduced from Europe.
Geographic distribution: Locally common throughout northern U.S. and southern Canada; south to Virginia, Missouri and Nebraska. Can be found in Colorado from 4000-7000'.
Ecological distribution: Often in saline substrates on lake shores, in sedge-rush, tamarix-sedge, rabbitbrush, pinyon juniper, and aspen to fir communities. Cultivated ground, waste places, and roadsides.
Soils: Mostly on sandy or gravely soils and alkaline soils.
Reproduction: Annual forb, reproduces by seeds. Flowers from June to August.
Germination: Germination may be inhibited in areas shaded by green plants. Seeds with incomplete germination can remain viable when moist or dry, but rapidly germinate when transferred to optimal conditions.


Conium maculatum L.
Poison hemlock, deadly hemlock, spotted water hemlock (Apiaceae)

Known locations in RMNP: Moraine Park, wet areas, fairly widespread in Park.
Assessment: A intermediate number of patchy distributed populations. When added together, all populations would cover less than 5 hectares. Plants appear to be having little impact on native communities or succession processes.
Origin: Introduced from Europe.
Geographic distribution: Throughout most of U.S. except for area between central Montana and northeast Minnesota. Reported throughout Colorado, but common in western half of state from 5000' to 9000'.
Ecological distribution: Along ditches, streams, rivers, and fence lines, woodland clearings, in wet and boggy meadows. Borders of pastures, cropland, gradually invades perennial crops, irrigation ditches, and wet ground along stream banks
Soils: Rich gravely or loamy soils, tolerates poorly drained soils.
Reproduction: Biennial forb, reproduces by seeds.
Germination: Fruits germinate mostly in autumn and in winter.
Control: Lorenz et al. (1987) suggest removal of individual plants by digging below basal leaves. Seed production in second year plants can be achieved by mowing prior to flower formation.
Chemical: Moderately susceptible to MCPA and 2,4-D. Poison hemlock can be selectively controlled in meadows and pastures by applying 2,4-D plus dicamba while the plants are young (Lorenz et al. 1987).
Notes: All plant parts, including taproot are poisonous.


Conyza canadensis (L.) Cronq. (Erigeron canadensis L.)
Horseweed, mare's tale, Canada fleabane (Asteraceae)

Known locations in RMNP: Persistent roadside weed in montane, common along roadsides.
Origin: Several sources indicate this species is a native of North American grasslands.
Geographic distribution: Common throughout North America, occurs in Colorado from 4000 to 7500'.
Ecological distribution: Fields, meadows, waste places. Often in riparian or other moist disturbed sites. Common in pastures, meadows, cultivated fields, along roadsides and waste places.
Soils: Commonly found on dry soils.
Reproduction: Annual or winter annual forb, reproduces by seeds. Flowers July to October.
Seed production: Average number of seeds is 50,000/plant. Seeds bear a "parachute" of some 25 toothed hairs.
Germination: Fruits germinate in autumn.
Control: Mowing infested meadows of pastures when the plant is in bud stage will prevent seed production.
Notes: Leaves and flowers contain a terpene which irritates the nostrils of horses.


Cynoglossum officinale L.
Houndstongue (Boraginaceae)

Known locations in RMNP: Two known locations in RMNP, Aspen Glen campground and Moraine Park.
Assessment: Currently does not appear to threaten native communities. Individual plants located in RMNP should be prevented from producing viable seeds because of potential for long distance seed dispersal.
Origin: Introduced from Europe.
Geographic distribution: Widespread and locally common in eastern U.S., infrequent west of the Great Plains. Found in cultivated areas in Colorado from 5000 to 9000'.
Ecological distribution: Pastures, waste fields. Bare and disturbed patches of stony or sandy ground.
Soils: Mostly on gravely, somewhat limy soils (between 2-50% calcium carbonate).
Reproduction: Biennial, of short lived perennial. Forms a rosette the first year and sends up a flowering stalk the second year. Reproduces by seeds. Flowers mid-May to July.
Seed dispersal: Nutlets break off at maturity, easily spread by clinging to animals fur and human clothing. In one experiment, many nutlets were found within 2 m of parent plant.
Seed longevity: Seeds may remain viable up to 3 years.
Seed production: Produces an average of 174-1823 nutlets/plant.
Germination: Requires spring vernalization (moist pre-chilling). Germination begins in late winter and early spring when temperatures rise above freezing point. Apparently no light requirement for germination.
Response to shade: Grows best in full sunlight, open space may be a prerequisite for its establishment.
Control: Young rosettes should be cut below crown with hoe or spade in early spring, mow flowering heads close to ground before seeds are formed.
Notes: Contains alkaloids, ingestion can lead to severe intoxication in cattle and horses.
References:

Delong, T.J., P.G.L. Klinkhamer, and L.A. Boorman. 1990. Biological flora of 
    the British Isles. Cynoglossum officinale. Journal of Ecology 78:1123-
    1144.

Descurainzia sophia (L.) Webb ex Prantl (Sisymbrium sophia)
Flixweed, pinnate tansy mustard. (Brassicaceae)

Known locations in RMNP: Skyland Ranch, East Portal, W. Moraine Park. Common roadside weed of disturbed areas.
Assessment: An intermediate number of patchy distributed populations in RMNP. When added together, all populations would cover an area less than 5 hectares. Flixweed appears to have little impact on native plant communities and on secondary succession processes.
Origin: Introduced from Europe.
Geographic distribution: Widely established throughout the U.S. and Canada. In Colorado found from 4000 - 8000'.
Ecological distribution: Roadsides, corrals, agricultural lands and other disturbed sites.
Reproduction: Spreads by seeds from early to late summer.
Seed production: Produces large numbers of seeds. By one estimate, a large plant produced about 700,000 seeds.
Seed longevity: Can remain viable in soil for relatively long periods.
Notes: Often a contaminant of the first cutting of alfalfa.


Dianthus aremeria L.
Deptford pink, grass pink (Caryophyllaceae)

Known locations in RMNP: Trailside between Cub Trail and Fern Lakes.
Origin: Introduced from Europe.
Geographic distribution: Widely established in North America. Locally common in eastern states. and Pacific Northwest.
Ecological distribution: Cultivated ornamentals, escaping. Sand or stony meadows, pastures and waste places. Front range foothills and Piedmont.
Reproduction: Annual or winter annual, reproduces by seeds. Flowers June to September.


Erodium cicutarium (L.) L'her
Redstem filaree, storksbill (Geraniaceae)

Known locations in RMNP: Crevice in blacktop parking lot, RMNP annex, Moraine Park.
Assessment: A few scattered populations in RMNP. When added together, populations would cover a total estimated area less than 5 hectares. Plants appear to be having little impact on native plant communities and on succession processes.
Origin: Introduced from Europe. native to Mediterranean region. Some accounts indicate plant may be native.
Geographic distribution: Widespread across North America, abundant on Pacific Coast. Scattered over Colorado except in extreme east from 4500 to 7500'.
Ecological distribution: Widely distributed herb in open sites and in numerous plant communities. A weed in fields and waste places, sometimes lawns, fields, pastures, and waste places, on dry soils.
Reproduction: Annual or winter annual, reproduces by seeds. Overwinters as rosette and blossoms in early spring. Flowers April to June and is one of earliest flowering plants in spring.
Seed dispersal: Seeds are wedge shaped with long humidity sensitive tail that coil into a tight spring when it is wet and uncoils when it is dry.


Erysimum cheiranthoides L. (Cheirinia cheiranthoides)
Treacle mustard, wallflower mustard (Brassicaceae)

Origin: Native to some parts of North America and also to Europe.
Geographic distribution: Widespread across northern U.S. and Canada.
Ecological distribution: Moist places in meadows, and along roadsides, sagebrush, grass, aspen, and spruce fir communities. Cultivated fields, waste places, meadows and disturbed areas.
Soils: Often on sandy or gravely soils.
Reproduction: Annual or winter annual, reproduces by seeds. Flowers June to August.
Reproduction: Plants may produce between 15,000 to 20,000 seeds/plant.
Seed longevity: Poor germination after one year of storage in sterile soil buried below the soil surface.


Festuca ovina L. (Festuca saximontana)
Sheep fescue (Poaceae)

Known locations in RMNP: Introduced for revegetation in RMNP, and has commonly been used in seed mixes.
Assessment: Several widespread and dense populations. When added together, all populations would cover an estimated area greater than 50 hectares. Generally, does not appear to be spreading. in planted areas. However, does not appear to inhibit secondary succession processes.
Origin: Turkish
Geographic distribution: Found throughout western U.S. in the Great Plains, in the Northeast, and in Mexico.
Ecological distribution: Often a dominant grass in forest openings, occupying mostly mesic sites. Chiefly in sagebrush, aspen-spruce-fir, ponderosa pine, lodgepole pine, and montane grass communities, and on exposed rocky slopes and ridges. Occasionally with pinyon juniper and mountain brush.
Note: Native strains of Festuca ovina are an important source of forage. F. ovina will thrive in areas where mean annual ppt. from 20-36 cm. Commercial strains have been developed from plants originating in Europe.


Festuca pratensis Huds.
Meadow fescue (Poaceae)

Origin: Native to Eurasia. Introduced to U.S. Found throughout most of North America.
Assessment: A few scattered populations in RMNP. When added together, all populations would cover an estimated area less than 5 hectares.
Ecological distribution: Introduced in pastures, roadsides, and valleys. Moist to dry sites, chiefly along roadsides and waterways in meadows, fallow-fields, and other disturbed sites. Occasionally in aspen spruce fir ponderosa pine, lodgepole pine communities, and on open slopes.
Notes: Meadow fescue is used as a pasture grass and for erosion control in the humid parts of the northern U.S. but it is neither high in yield nor as persistent as F. arundinaceae.


Hieracium aurantiacum L.
Orange hawkweed (Asteraceae)

Known locations in RMNP: East of Endovalley picnic area, 8600'. Recently introduced into RMNP, probably as part of a roadside beautification mix.
Assessment: A few scattered populations found in park. When all populations are added together, would cover a total area less than 5 hectares. Found mostly in sites disturbed in last 3 years.
Origin: Europe.
Geographic distribution: Limited, reported to be west of the Cascades into northwestern Wyoming. Increasingly troublesome in north-central states. Becoming established along foothills of Colorado.
Ecological distribution: Old fields, meadows, pastures and lawns.
Soils: On dry sterile gravely, mostly acidic soil.
Reproduction: Perennial, reproduces by seeds and runners. Flowers July to August.
Control: Dicamba (Banvel) at 0.25 to 0.75 lb. ai/A. is listed for control of H. aurantiacum in established lawns and turf.


Lactuca serriola L. Lactuca scariola L.
Prickly lettuce, wild lettuce (Asteraceae)

Origin: Introduced from Europe.
Known locations in RMNP: Documented by Denver Botanical Garden in Montane uplands in 1991.
Assessment: A few scattered populations in RMNP. When added together, all populations would cover an estimated area of less than 5 hectares. Plants appear to be having little effect on native plant communities or secondary succession processes.
Geographic distribution: Widespread and locally abundant throughout the northern U.S. and southern Canada. In Colorado widespread, most common in north-central area, 4500-6000'.
Ecological distribution: Cultivated fields, waste places. Common along roadsides, yards, and small gardens. Disturbed habitats, fence rows, and overgrazed pastures.
Soils: Usually on light or dry soils.
Reproduction: Winter annual or biennial forb, reproduces by seeds. Flowers July to August.
Seed longevity: Good viability after 3 years burial below soil surface.
Seed dispersal: Seeds bear parachute-like pappus.
Germination: Fluctuating temperatures of 20-30 degrees in dark light conditions resulted in 92% germination.
Level of impact: Invades lower elevation rangelands where it is eaten by wildlife and livestock. Serious invader of disturbed soils of irrigated crops and orchards.
Notes: Pulmonary emphysema may develop in cattle feeding extensively on this weed.


Lappula occidentalis var. occidentalis (S. Wats) Lappula redowskii (Hornem.) Greene
Beggar's tick, western sticktight (Boraginaceae)

Origin: Native to western plains region, however not known to be native to RMNP.
Known locations in RMNP: Beaver Point, Hidden Valley Ranch, Eagle Cliff Mountain, and Hollowell Park.
Ecological distribution: Along roadsides, waste areas, and abused ranges.
Reproduction: Annual forb, reproduces by seeds.
Seed dispersal: Seeds cling to animal fur, and clothing for dispersal.


Lepidium campestre (L.) Ait.f. (Neolepia campestre)
Field cress, field pepperweed (Brassicaceae)

Origin: Introduced from Europe.
Known locations in RMNP: Moraine Park.
Assessment: An intermediate number of patchy distributed populations in RMNP. When added together, all populations would cover an estimated area less than 5 hectares. Field cress appears to be having little impact on native plant communities and secondary succession processes.
Geographic distribution: Widespread and locally abundant throughout northeastern and north-central states and Ontario, infrequent elsewhere.
Ecological distribution: Roadsides and other disturbed sites. Grain fields, new seedlings of clover or alfalfa. and wastelands.
Reproduction: Biennial or winter annual, reproduces by seeds. Flowers June to July.


Lepidium densiflorum Schrad. L. bourgeauanum, L. fletcheri, L. neglectum
Peppergrass, green flower pepperweed

Origin: May be introduced from Europe, although many sources indicate this species is native to North America.
Known locations in RMNP: Beaver Point, Lower Black Canyon.
Geographic distribution: Widespread throughout U.S. and southern Canada, common in west and mid-west. Found in Colorado from 5000 to 7500'.
Ecological distribution: Warm desert shrub, salt desert shrub, salt grass, sagebrush, pinyon juniper, ponderosa pine, aspen and spruce-fir communities. Grain fields, neglected fields, plains, prairies, and waste places.
Soils: Especially on light, sandy soils.
Reproduction: Annual or winter annual, reproduces by seeds. Flowers April to July (sometimes in May).
Seed dispersal: When mature, plant can become a tumbleweed.


Lepidium perfoliatum L.
Clasping pepperweed, peppergrass (Brassicaceae)

Origin: Introduced from Europe.
Geographic distribution: Has become established in much of the U.S., abundant and troublesome in Great Basin, but appears locally from New York to the Pacific. Western U.S., and over half of Colorado up to 8500'.
Ecological distribution: Often in disturbed sites, in creosote bush, blackbrush, other warm desert shrub, shadscale, greasewood, galleta, pinyon juniper, and sagebrush communities. Grows in grain fields, pastures, and waste places. Fields, dry prairies, roadside weed of warm valleys.
Reproduction: Annual or biennial, reproduces by seeds. Flower and seed production occur from April to June, seeds are formed in early spring.
Seed longevity: Seeds are long-lived in cultivated soils.
Germination: Peak germination occurs in fall.


Lolium perenne L. (Lolium multiflorum)
Perennial ryegrass, Italian ryegrass (Poaceae)

Assessment: Used for an experiment on road shoulders, most plants used in experiment are no longer present.
Origin: Europe.
Geographic distribution: Throughout northern U.S.
Ecological distribution: An escape from cultivation, in dry to moist sites, along waterways, fallow fields, and on open grassy slopes. Common weed of roadsides, waste areas and cultivated crops. Frequently found on foot trails and road ways where there is a reasonable amount of treading and/or grazing. Does well in areas with cool moist summers.
Soils: Especially on fertile soils, the ideal soil is a deep fertile loam with a good humus content. A relatively wide pH tolerance (5.0-8.0), optimal pH is 6.0-7.0. Can become established in native soils (in England) only if lime has been applied.
Reproduction: Perennial, reproduces by seeds and does not produce rhizomes or stolons. Blooms June to July.
Seed production: An efficient seed producer.
Seed dispersal: Because seeds are relatively heavy and compact, dispersal is limited to areas in close proximity to the parent plant.
Seed longevity: Seeds will survive as long as soil moisture is adequate. Stored seeds (kept in paper packets) remained viable up to 8 years. However, percent germination rapidly dropped off after 5 years.
Germination: Germination in laboratory conditions can reach 90-95%, but these values are rarely attained in the field.
Control: To destroy, hand pull, but wear gloves.
Chemical: In crops, dalapon has been used to control established plants, and trifluralin prevents seedling establishment. Herbicides which have been used to control L. perenne include in small grain and grass crops include alachlor, benefin, diphenamid, fluazifop-butyl, isoporpalin, sethoxydim, or terbacil.
Notes: Sometimes used as a temporary turf pasture grass, becoming a troublesome weed in lawns because it resists mowing. Ryegrass is thought to have been the first meadow grass to have been cultivated in Europe, records of its use date back to 1681. Now widely used for pasture, hay lawns, and erosion control in most North America and temperate South America.
References:

Beddows, A.R. 1967. Biological flora of the British Isles: Lolium perenne L. 
    Journal of Ecology 55: 567-587.

Lychnis alba Mill. (Melandrium album, Silene alba)
White campion (Caryophyllaceae)

Origin: Naturalized from Eurasia.
Known locations in RMNP: MacGregor's Ranch, Husted's Ranch, bottom of Black Canyon, Estes Park Headquarters.
Assessment: An intermediate number of patchy distributed populations in RMNP. When added together, all populations would cover an estimated area less than 5 hectares. Does not appear to be readily dispersed in RMNP, and appears to have little effect on native plant communities.
Geographic distribution: Widespread in North America. Widespread and locally common, in eastern states and Pacific Northwest.
Ecological distribution: Open sites, often in indigenous vegetation. Borders of fields, waste places and roadsides. Troublesome weed in grain and legume fields. Common weed in mountain pastures.
Soils: Common on rich, well-drained soils.
Reproduction: Biennial or short lived perennial, reproduces by seeds and short rootstocks. Flowers late May to September.
Seed production: May produce as many as 5000 seeds to 15,000 seeds but germination may be as low as 10 percent.
Germination: Dry storage for 10 months, or pre-chilling 1 week at 5 C improved germination.
Control: Scattered plants should be pulled or hoed off early to prevent seed production.
Chemical: Herbicides that may be used to control white cockle include bentazon, bromoxynil. chlorosulfuron. methazole, terbacil and terbutryn.


Matricaria matricaroides (Lepedotheca suaveolens, Matricaria discoidea)
Pineapple weed, rayless chamomile (Asteraceae)

Origin: Native to Pacific Coast and eastward to Montana and Wyoming. Introduced into the northeastern states and spreading rapidly.
Known locations in RMNP: Ditch across from Holzworth ranch. Common on disturbed soil, especially unpaved areas. Plants mostly found in areas where fill materials from outside of park were used.
Assessment: A few scattered populations in RMNP. When added together, all populations would cover an estimated area less than 5 hectares. Plants appear to be having little effect on native communities or secondary succession processes.
Geographic distribution: From Alaska to Baja California and east to Montana and Arizona. Now in the Atlantic states, especially near towns and cities.
Ecological distribution: Grains, fields, farm yards, waste places and roadsides.
Reproduction: Annual, reproduces by seeds. Flowers May to September.
Seed production: Each flower head produces an average of 135-160 fruits, the average fruit productions is nearly 7000.
Seed dispersal: May be dispersed in mud, and by rainwash, or by adhering to boots and tire treads.
Control: Pineapple weed resists a number of standard weed killers such as 2,4-D and MCPA, but is moderately sensitive to sulfuric acid applied to the foliage. Somewhat sensitive to a combination of MCPA and 2,3,6 TBA.


Matricaria perforata Merat. (Matricaria inodora)
Wild chamomile, scentless chamomile Asteraceae

Origin: Introduced from Europe, native origins thought to be in the Caucasus Mountain region.
Geographic distribution: Distributed in the northwestern north-central and northeastem U.S., the Great Plains with the most southerly locations being Kansas and Missouri.
Ecological distribution: Disturbed ground, especially montane roadsides, pastures, and townsites. Annual and perennial crops, wasteland, lawns, gardens, fence lines, and ditches. Often associated with low lying areas that are poorly drained.
Soils: Found in a range of soils including clay, clay loam, loam and fine sandy loam. Soils with organic matter ranges from 2.7-35.4% and pH ranges from 5.5-7.9. Generally not tolerant of heavy calcareous soils.
Reproduction: Annual to short-lived perennial, reproduces entirely by seed.
Seed dispersal: Seeds are dispersed by both wind and water. Seeds also remain viable after passing through digestive tracts of animals.
Seed production: Produces from 1800 to 36,000 seeds per plant.
Seed longevity: Seeds may remain viable in soil for up to 10 years.
Germination: Light is important for germination of freshly harvested seeds, but is less important for seeds that have been stored.
Competition: Plant may spread in areas of minimal competition, reduces yield in some crops.
Control (mechanical): Mowing can be used to control scentless chamomile. In order to reduce seed production, plants should be mowed in the vegetative stage prior to anthesis.
Chemical: Several herbicides are effective for controlling scentless chamomile. In native blue grass communities, picloram applied at 0.14 kg/ha or dicamba applied at 1.1 kg/ha effectively controlled scentless chamomile one year after fall application. Studies have also found that picloram applied at 0.28 kg/ha effectively controlled plants that were 25 cm tall.
References:

Kay, Q.O.N. 1994. Biological Flora of the British Isles. Tripleurospermum inodorum 
    (L.) Schultz Bip. Journal of Ecology 82:681-697.

Woo, S.L., A.G. Thomas, D.P. Peschken, G.G. Douglas, V Harms, and A.S. McClay. 1991. 
    The biology of Canadian weeds. 99. Matricaria perforata Merat (Asteraceae). 
    Canadian Journal of Plant Science 71:1101-1119.

Medicago lupulina L.
Black medic, hop clover, yellow trefoil (Fabaceae)

Known locations in RMNP: Moraine Park picnic area, Cub Lake.
Origin: Introduced from Europe.
Geographic distribution: Worldwide distribution, found in Colorado up to 8000'.
Ecological distribution: Lawns, fields, meadows, waste places, along roadsides, and waste areas.
Reproduction: Annual, possibly short-lived perennial, reproduces by seeds. Flowers from April to September.
Seed longevity: Seeds can remain viable up to 5 years.
Seed germination: Germination promoted with the presence of light, optimum temp. between 17-18 C.
Notes: A frequent contaminant of uncleaned alfalfa and clover seed. Quickly and rapidly spreads.


Mentha spicata L.
Spearmint, lambmint, garden mint (Lamiaceae - Labiatae)

Origin: Introduced from Eurasia.
Known locations in RMNP: Leving's Spring (Long's Peak district)
Assessment: A few scattered populations in RMNP. When added together, all populations would cover an estimated area less than 5 hectares. Found in areas disturbed in the last 11-50 years. Does not appear to be affecting native plant communities or secondary succession processes.
Geographic distribution: Widely distributed in North America. Common in north-central states, also Pacific Coast.
Ecological distribution: Cultivated aromatic herb, escaping and now established along streams and canal banks and other moist sites. Moist pastures and range places.
Reproduction: Perennial, reproduces by creeping rootstocks.
Notes: Cultivated in some localities for the oil of spearmint.


Onobrychis viciaefolia Scop. (Onobrychis saliva, Hedysarum onobrychis)
Sanfion (Fabaceae)

Origin: Native to Europe, found mostly in southern Europe.
Known locations in RMNP: Roadside near MacGreggor's Ranch.
Ecological range: Introduced forage plant, escaping and persisting and some areas. Long lived on dry land, but short-lived on irrigated lands.
Soils: Especially well adapted to dry calcareous soils of northern Rocky Mountain region.
Reproduction: Perennial forb.
Notes: Adapted as a range legume in areas with 13" or more precipitation, frost tolerant and drought resistant. May have value as a range crop.


Phleum pratense L.
Timothy, Herd's grass (Poaceae)

Assessment: Populations are widespread in RMNP. When added together, all populations would cover an estimated area larger than 50 hectares. Plants have potential to inhibit secondary succession processes, and may modify native communities.
Origin: Europe.
Geographic distribution: Temperate regions. Grows well in the humid climate of the northeast and south into the cotton belt, coastal regions of Pacific N.W., valleys Rocky Mountains. Introduced to America because of its value as a hay and pasture grass.
Ecological distribution: Roadsides, along waterways, in dry to wet meadows, in aspen-spruce-fir communities, occasionally in oak-sagebrush, pinyon juniper, mountain brush and ponderosa pine communities. Roadsides, meadows, pastures. Humid regions of the U.S., open lots, adapted to cool climates, but not drought conditions.
Soils: Adapted to clays and lightly textured soils.
Reproduction: Perennial bunchgrass, reproduces by seeds and is self-sterile. Blooms in June and July.
Level of impact: It is both cold and shade tolerant, but vulnerable to drought, high temperatures, and grazing.
Competition: Often seeded with other plants such as legumes without reducing yields.
Control: Wear gloves to pull this large grass out. Frequent cutting or mowing can weaken overall plant health.
Chemical: Apply Paraquat, grass is moderately sensitive to in lower doses and very sensitive at higher doses.
Note: Important hay grass in U.S., escaped from cultivation.


Plantago major L.
Broadleaf plantain, common plantain (Plantaginaceae)

Origin: Europe, possibly a native of Northwest.
Known locations in RMNP: Administration building, utility site.
Assessment: A few scattered populations found mostly in disturbed areas. When added together, all populations would cover an area less than 5 hectares. Plants appear to be having little effect on native plant communities or succession processes.
Geographic distribution: Throughout North America, cosmopolitan in distribution. In Colorado occurs from 3500' to 9000'.
Ecological distribution: Widespread weedy species of lawns, fields and other disturbed areas. Pastures, meadows, open woods, lawns, waste places. Roadsides, cultivated fields, and can be found in valleys to mid montane sites.
Soils: Most common on rich. somewhat moist soils. Occupy a wide range of soils such as loam, clay, and sand. Plants are relatively resistant to compaction.
Reproduction: Perennial herb, reproduces by seeds and new shoots from roots. Can reproduce from cut pieces of roots. Reproduction is primarily by seed, although plant is capable of vegetative reproduction. Flowers are wind pollinated, and are self-compatible. Flowering occurs from June to September.
Seed production: Reported seed production ranges from 565 to 14,000 seeds/plant. Between 60-90% germination of seeds is common.
Seed longevity: Seeds may remain viable in soil up to 40-60 years.
Seed dispersal: Medium potential for dispersal based on seed weight and seed shape. A common impurity of crop seed. Seeds also possess a sticky mucilaginous cover that causes them to stick to soil particles or adhere to feathers, fur or skin.
Germination: Very long period of dormancy, some seeds germinate in early spring, but many germinate later in growing season. Germination in the laboratory was highest with longer photoperiods (16 hour).
Response to shade: Usually only prevalent in grasslands where turf is short. Rarely found is shaded areas or areas that are continually wet during the growing season. Generally does not become established unless surrounding vegetation is short.
Control: Broad leafed plantain does not root deeply, and the plants can be pulled with relative ease. Pull before the flowering scape matures.
Chemical: Any strong acid such as carbolic will kill these perennials. Plantains are generally susceptible to 2,4 D, 2,4,5-T, MCPA, fenoprop, and to greater applications of 2,4-DB, MCPA, and dicamba. A single application of MCPA salt or 2,4-D (twenty four ounces per acre) will kill these perennials.
References:

Hawthorn, W.R. 1974. The biology of Canadian weeds. 4. Plantago major and P. 
    rugelii. Canadian Journal of Plant Science 54:383-396.

Poa annua L.
Annual bluegrass, annual speargrass (Poaceae)

Origin: Native to Eurasia and western North America.
Geographic distribution: Widespread and common in U.S., widely distributed throughout Colorado from 5000' to 9500'.
Ecological distribution: An invader of lawns and moist, open waste places. Occasionally in salt desert shrub, sagebrush, oak maple, aspen fir, lodgepole pine, and meadow communities. Gardens, cultivated crops, roadsides, ditches and pastures. A very adaptable species found in a variety of climatic conditions.
Soils: Common on moist, rich soils. Found on most soil types, and tolerates trampling, mowing, and poorly aerated soils. Lacks tolerance to highly acidic soils (below pH of 5.3), pollution, and extremes of temperature and moisture.
Reproduction: Annual, or short lived perennial, reproduces by seeds. Flowering and seed production occurs from April to June, thrives best in cool weather of spring. Plant is self-fertile. Fruits can be produced almost all seasons, and several generations may succeed one another in a single year.
Seed production: Plants average 80 viable seeds/inflorescence with 30-450 inflorescence produced per plant. Seed viability is generally high.
Seed dispersal: Low-medium potential for dispersal based on seed weight and seed shape. Carried in mud on boots, animal hoofs, etc. Seeds are also likely dispersed by rain, wind, and birds. Seeds remain viable after passing through the digestive tracts of some animals such as cows, horses, and deer.
Germination: Seeds may germinate any time of the year, but germination is highest from May to June.
Competition: Generally does not compete strongly with established plants.
Control: Grass is resistant to both MCPA and 2,4-D.
Chemical: Presently, there are no herbicides available that are specific to annual bluegrass. The most commonly used pre-emergence control measures include bensulide, and chlorothaidimethyl. Commonly used postmergance herbicides include endothal, linurom, and tricalcium arsenate.
Mechanical: Can tolerate severe defoliation. Cutting annual bluegrass below 0.5 to 1.0 cm increases seedling vigor and increases the competitive ability of this grass.
References:

Hutchinson, C.S. and G.B. Seymour. 1982. Biological flora of the British Isles. 
    Poa annua L. Journal of Ecology  70:887-901.

Warwick, S.I. 1979. The biology of Canadian weeds. 37. Poa annua L. Canadian 
    Journal of Plant Science 59:1053-1066.

Poa bulbosa L.
Bulbous bluegrass (Poaceae)

Assessment: A few scattered populations in RMNP. When added together, all populations would cover an estimated area less than 5 hectares. Bulbous bluegrass appears to be having little impact on native plant communities or secondary succession processes.
Origin: Europe, native of Eurasia and North Africa.
Geographic distribution: Scattered throughout most western states.
Ecological distribution: Moderately dry to moist sites. A weed of cultivated and waste areas in sagebrush, oak maple, and streamside communities. Pastures, grain fields, roadsides. Commonly used as a pasture grass and for erosion control.
Reproduction: Perennial, grows from basal buds.
Notes: Commonly cultivated. Bulbous blue grass produces palatable forage soon after snow melt, but total production is low and growing period is short. The species has been used to some extent for pastures and for erosion control in parts of the west, having been adapted for use as an understory grass in range seeding of wheatgrass and other dryland grasses.


Poa compressa L.
Canada bluegrass (Poaceae)

Assessment: A few scattered populations in RMNP. When added together, all populations would cover an estimated area less than 5 hectares. Canada bluegrass appears to have little impact on native plant communities and secondary succession processes. Canada bluegrass has similar biology, ecology, and control methods to Poa pratensis.
Origin: Native to Europe, Eurasia. Introduced to North America as a forage grass.
Geographic distribution: Widespread throughout North America.
Ecological distribution: Commonly found on dry hillsides. Mesic to wet sites in pastures, along waterways, in open places. In sagebrush, juniper, oak-maple, aspen, ponderosa pine, and lodgepole pine communities, often in the wake of disturbance. Most prevalent on drier sites. In the more humid regions of the U.S., Canada bluegrass is employed for use as a pasture grass and for erosion control.
Soils: Well adapted to most soils, and common on acidic, infertile, coarse textured and rocky soils.
Reproduction: Perennial grass, reproduces by seeds and rhizomes.
Germination: Pre-chilling (at 10 C for 10 days) followed by alternating temperatures increases germination.
Control: Also see control information for Poa pratensis.
Mechanical: Mowing is an ineffective method of control. Early spring grazing can be used to increase competition from warm season grasses.
Chemical: Aresenal (imazapyr) has been used to control Canada bluegrass.
Other: Fire can be used in late spring, although this method may be less effective with Canada bluegrass than Kentucky bluegrass. Prescribed burns in the fall have resulted in increased reproductive culms in Canada bluegrass.


Polygonum arenastrum Jord. ex Bor. Polygonum aviculare ssp. arenastrum
Knotweed, Devil's shoestrings

Origin: Native of North America, but also may be introduced from Eurasia.
Geographic distribution: Common throughout northern U.S. and southern Canada.
Ecological distribution: Open waste grounds, roadsides, heavily disturbed areas, lawns, cropland. Common on hard, trampled ground.
Soil: Plant is resistant to trampling.
Reproduction: Summer annual herb, reproduces by seeds. Flowers June to October.
Seed dispersal: Low potential for dispersal based on seed weight and seed shape.
Germination: For Polygonum sp., seed embryos are rudimentary (not fully developed) when seed falls. The seed will not germinate until growth is complete. Optimal germination temperatures are between 8-12 C during spring. Seeds require high temperatures and relatively long periods of soil moisture for seed germination.
Control: In lawns or turf areas, improved management techniques which improve competition from other species can help control knotweed. A mixture of 2,4-D plus dicamba can be used for these areas. Atrazine, chlorpropham, and cynazineare recommended for control in various crops. Mixtures of 2,4-D plus dicamba can be used in waste areas.


Polygonum convolvulus (L.) (Fallopia convolvulus)
Black bindweed, wild buckwheat (Polygonaceae)

Origin: Europe
Geographic distribution: Widely distributed throughout U.S. and North America, probably introduced as a crop contaminant.
Ecological distribution: Weedy species of gardens, fields, and other open habitats. Cultivated fields, gardens, orchards, non-crop areas, waste areas, disturbed sites. Adapted to a wide range of climatic conditions.
Soils: Found in most temperate agricultural soils.
Reproduction: Annual reproduces by seeds. Plant is self-compatible. Flowers from June to September.
Seed production: 11,900-30,000 seeds/plant.
Seed dispersal: Seeds can be dispersed by farm machinery and water over short distances. Wild buckwheat is also a common contaminant of wheat and other cereal crops.
Germination: Most viable seed germinates in the first year. Seeds can remain viable up to 5 years in soil.
Competition: Reduces crop yield through competition, especially in areas of dense stands. The climbing habit of this plant allows it to obtain light while growing in stands of grains or other tall crops. Has the ability to spread rapidly, and quickly cover bare ground. Generally a good competitor in areas of high fertility. Roots are efficient at absorbing water and soil nutrients.
Control: A number of chemicals are recommended for use in controlling wild buckwheat. Dicamba plus MCPA or 2,4-D, or bromacil plus MCPA are recommended for use in small grain crops. In non-crop areas, dicamba, bromoxynil in combination with 2,4-D or MCPA can be used for selective control without injury to grasses.
References:

Hume, L., J. Martinez K. Best. 1983. The biology of Canadian weeds. 60. Polygonum 
    convolvulus L. Canadian Journal of Plant Science 63 :959-971.

Potentilla norvegica L. (Potentilla monospeliensis)
Norway cinquefoil, rough cinquefoil (Rosaceae)

Assessment: Norway cinquefoil is likely a planted ornamental. A few scattered populations in RMNP. When added together, populations would cover an estimated area of 5-10 hectares. Plants appear to be having little impact on native plant communities or secondary succession processes.
Origin: Eurasia
Geographic distribution: Widely distributed in North America. Throughout all of U.S. except southeastern and southwestern areas.
Ecological distribution: Flood plains, wet meadows, lake shores and other moist sites. Fields, old pastures, roadsides, waste places.
Reproduction: Annual or biennial, reproduces by seeds. Flowers from June to October.
Control: Herbicides which are normally used to control broadleaf weeds have been used to control Norway cinquefoil in crops. In pastures, management which improves competition from other species is recommended.
Chemical: 2,4-D plus dicamba in the early spring after active growth has been initiated can be used in pastures. Repeated applications may be necessary. In waste areas and along fence rows, 2,4-D, MCPA, or dicamba can also be used for selective control.


Psatlhyrostachys juncea (Fisch.) Nevski (Elymus junceus)
Russian wildrye (Poaceae)

Origin: Introduced from Russia. Russian wildrye was first introduced into the northern Great Plains in 1927 as a pasture grass and for use in erosion control.
Ecological distribution: Well adapted to northern plains and inter-mountain states. Salt desert shrub, sagebrush, pinyon juniper, mountain brush, aspen, and ponderosa pine communities.
Soils: Grows best on loam and clay and tolerates saline soil.
Reproduction: Perennial, reproduces by seeds. Russian wild rye has low seedling vigor and poor seed production.
Notes: Grows rapidly in early spring and endures close grazing relatively better than most grasses. The species is useful because of its drought resistance and salt tolerance. Widely cultivated for range stabilization.


Rheum rhubarbarum L.
Rhubarb

Assessment: A few scattered populations in RMNP. Although rhubarb is persistent, does not pose a threat to native plant communities or secondary succession processes. Little information is available on rhubarb outside of its value as a crop.
Ecological distribution: Cultivated fruit, persisting in some areas.
Notes: The plant is used alone and mixtures of fruits to make pies, jams, jellies, and beverages.


Rumex acetosella L. (Acetosella vulgaris)
Sheep sorrel, red sorrel, field sorrel, sour dock (Polygonaceae)

Assessment: An intermediate number of patchy distributed populations. When added together, all populations would cover an estimated area of 5- 10 hectares. Found mostly in areas disturbed in the test 10 years. May inhibit the establishment of native species.
Origin: Eurasia.
Geographic distribution: Throughout U.S., reported in north-central, central and south central Colorado from 4500' to 10,000'.
Ecological distribution: Roadsides, meadows and other open sites. Gardens, pastures, meadows, lawns, persists in areas of poor drainage and low soil fertility, abundant in disturbed areas and sites of recent fires.
Soils: Often an indicator of acidic soil, also thrives in neutral or slightly alkaline soils
Reproduction: Perennial forb, reproduces by seeds and creeping rhizomes. Extensive, rapidly spreading rhizomes. Flowers from June to August.
Seed production: 250 seeds/plant.
Seed dispersal: Medium potential for dispersal based on seed weight and seed shape.
Control: Very difficult to eradicate, soil amendments such as lime actually disfavor this calcifuge species.
Chemical: A mixture of 2,4-D and dicamba or glyphosate applied when young plants are actively growing can be used in pastures and lawns.


Rumex crispis L.
Curly dock, sour dock, yellow dock (Polygonaceae)

Assessment: Commonly found in disturbed areas. When added together, all populations would cover an estimated area less than 5 hectares. Curly dock may inhibit secondary succession processes in some open areas.
Origin: Eurasia.
Geographic distribution: Found throughout the U.S. and Canada, throughout Colorado from 3500 to 8500'.
Ecological distribution: Weedy plant of open sites. Pastures, hayfields, meadows, waste areas and gardens, especially common in wet meadows, along ditchbanks and in waste areas. Open areas in pasture or other areas are adequate sites for establishment.
Soils: Grows vigorously on moist soils. Found on most soils including well and poorly drained, clay, loamy clay, fertile, and slightly acid soils. Seldom found on acidic soils.
Reproduction: Perennial herb, reproduces by seeds and root fragments. Vegetative multiplication occurs readily. Flowers April-July.
Seed production: 29,500-60,000 seeds/plant, with up to 88% germination in good light.
Seed longevity: 52% germination has been observed in seeds that are 50 years old, and some seeds may remain viable up to 80 years.
Seed dispersal: Seeds can be wind dispersed, however, many seeds fall near the parent plant. Seeds are buoyant, and can be water dispersed. Seeds remain viable after passing through the digestive tracts of birds and cattle. Seeds may also stick in animal coats and human clothing.
Germination: Seeds have a high germination, scarification is not required. Soil disturbance stimulates germination. Seeds require light, alternating temperatures, or both for germination.
Competition: Seedlings grow best in open areas, and do not withstand crowding by more vigorous species.
Control: Seeds should be removed before plant comes to fruit.
Mechanical: Scattered plants can be mechanically removed with a spade.
Chemical: MCPA salt (sixteen ounces per acre) and 2,4-D amine can be used to help control this plant.
Notes: If large amounts are consumed by cattle, the animals may suffer dermatitis and gastric distress.
References:

Cavers, P.B. and J.L Harper. 1964. Biological flora of the Bristish Isles. Rumex 
    obtusifolia L. and R. crispus. Journal of Ecology 52: 754-766.

Salsola iberica Senn. & Pau. (Salsola kali ssp. tragus (L.) Aellen, Salsola australis)
Russian thistle (Chenopodiaceae)

Origin: Native to Eurasia, introduced from Russia.
Known locations in RMNP: Beaver Point, Hidden Valley Ranch.
Assessment: A few scattered populations in RMNP. When added together, all populations would cover an estimated area less than 5 hectares. Appears to be having low impact on plant communities and succession processes.
Geographic distribution: Chiefly in dry regions of western U.S., western Canada, and north-central states. Widespread over Colorado up to 8500'.
Ecological distribution: Grows on dry plains, in cultivated fields, waste places, roadsides, railroad rights of ways, chiefly in grain growing areas. Well adapted to dry land agriculture, but also found on disturbed waste areas and some irrigated croplands. An early succession species adapted to disturbed land.
Soil: Adapted to disturbed soil, but germination greatly reduced in compact soil. Drought resistant, and does well on neutral and saline soils.
Reproduction: Annual, reproduces by seeds. Flowers July through October.
Seed production: A single plant can produce 100-200,000 seeds.
Seed dispersal: At maturity, plants break off at base and become tumbleweed, disperses seeds long distances.
Seed longevity: Residual seeds do not seem to be an important factor in the establishment of these plants. Nearly 100% of the current years crop germinate the first year. However, some reports indicate that seeds may remain viable for several years.
Germination: Rapid germination and seedling establishment occur after only brief and limited amounts of precipitation. Seeds germinate at low moisture over wide temperature ranges.
Competition: Although roots are extremely efficient, Russian thistle plants do not do well in competition with other species. Both intra- and inter-specific competition can reduce the ability of these plants to set seed.
Level of impact: Russian thistle produce tumbleweeds that can obstruct waterways and cause fire hazards. Russian thistle generally relies on disturbances such as land clearing, tillage, grazing, fire, and drought to remain established. If these disturbances are controlled, Russian thistle will eventually be replaced by other species.
Control: Russian thistle infestations can be reduced by maintaining natural plant cover and promoting the re-establishment of native species in infested areas.
Chemical: Numerous herbicides have been used to control Russian thistle. Banvel (dicamba) applied at the rate of 0.5-1.5 pt/acre is commonly used against broadleaf weeds. Chiptox 2E (MCPA salt), 2,4-D Amine, and Paraquat can all be used depending on the location of the weeds.
Mechanical: In small areas, mechanical weed control such as hand pulling young plants, or cutting offplants just below the crown can help reduce seed formation. Mowing is also commonly used against tall annuals to control seed production. However, mowing should be used with care because it can reduce growth and development of desirable species and favor the establishment of additional exotic species.
Biological control: A number of species of insects (including two moths) have been studied for their potential as biological control agents. No single species has been effective in establishing viable populations and controlling Russian thistle.
Notes: There is some indication that Russian thistle is autotoxic. This may help to explain why the plant disappears with time from the weed stage after it has established itself in an area.
References:

Crompton' C.W. and l.G. Bassett. 1985. The biology of Canadian weeds. 65. Salsola 
    pestifer A. Nels. Canadian  Journal of Plant Science. 65:379-3X8.

Fithian, J. 1988. Element stewardship abstract for Salsola iberica (Russian 
    thistle). The Nature Conservancy, Minneapolis.

Sisymbrium altissimum L.
Jim Hill mustard, tumble mustard (Brassicaceae)

Known locations in RMNP: Moraine Park.
Origin: Introduced from Europe.
Geographic distribution: Widely distributed in U.S., especially troublesome in northwestern U.S. Found throughout Colorado to 8500'. Disturbed sites, but often in indigenous habitats. Grows in grain fields, cultivated fields, roadsides, and waste places.
Reproduction: Annual or winter annual forte, reproduces by seeds. Flowers June to September. Jim Hill mustard is a prolific seeder, but seedlings may die before growth is established.
Seed production: One large plant was estimated to produce 30,000 seeds.
Seed longevity: Relatively few seeds remain dormant in cultivated soils for longer than 6 years.
Seed dispersal: Stem breaks off at maturity causing the plant to be blown by wind, scatters seeds as it blows.
Germination: Peak germination in spring, with less pronounced peak in fall. Seeds germinate at any temperature following maturity (0-20 C).
Notes: Common in recently disturbed areas, but likely to diminish in its abundance and frequency over time.


Sisymbrium officinale (L.) Scop.
Common hedge mustard (Brassicaceae)

Origin: Introduced from Europe.
Geographic distribution: Common throughout U.S. and Canada.
Ecological distribution: Uncommon weed of disturbed sites. Fields of small grain, gardens, waste places.
Reproduction: Annual or winter annual herb' reproduces by seeds. Flowers June to September.
Seed production: Large plant estimated to produce more than 9500 seeds.
Germination: Germination occurs in April in the field, both fresh and old seed may require pre-chilling.
Control: Cynazine is the only herbicide specifically labeled for control of hedge mustard. Very susceptible to application of 2,4-D. Readily controlled by hormone type herbicides, but the adult plant exhibits a greater resistance to herbicides.


Solanum triflorum Nutt.
Cut leafed nightshade, wild tomato

Origin: Native to North America.
Reproduction: Annual. reproduces by seeds.
Geographic distribution: Found over Colorado from 3500 to 9000'.
Ecological distribution: Prairies, cultivated fields. pastures, gardens, waste areas.
Notes: The berries of Solanum triflorum are poisonous.


Spergularia rubra (L.) (Tissa rubra)
Red sandspurry (Caryophyllaceae)

Origin: Introduced from Europe.
Known locations in RMNP: Bear Lake parking lot (growing in asphalt cracks).
Geographical distribution: Newfoundland to British Columbia, south to Alabama and California.
Ecological distribution: Common along logging trails, only species in mountains. Mixed conifer, lodgepole pine, and meadow communities. Especially on pond, stream, and lake shores and margins, but also on roadsides.
Soils: Wasteland weed on sandy or gravely soils.
Reproduction: Annual or short-lived perennial, reproduces by seeds. Flowers April to October.
Germination: Fluctuating temperatures (20-30 C) with alternating light yielded 52% germination.
Control: Hand pull or hoe to prevent germination.


Taraxacum officinale Weber. in Wiggers (Taraxacum vulgare)
Dandelion, Lion's tooth, blowball Asteraceae

Origin: Introduced from Eurasia. According to some authorities, native to North America.
Known locations in RMNP: Beaver Meadows, Poudre Lake, abundant in wet meadows in springtime from montane to sub-alpine.
Assessment: An intermediate number of patchy distributed populations. When added together, all populations would cover an estimated area greater than 50 hectares. Dandelion appears to be having little impact on native plant communities or secondary succession processes.
Geographical distribution: Widespread throughout North America from sea level to 12,000'. In Colorado from 4500 to 9500' or more.
Ecological distribution: Grows on moist sites including lawns, meadows, pastures, and over-grazed areas. Hayfields, often an impurity of Kentucky blue-grass and forage seeds.
Soils: Flourishes on a diversity of soil types, especially on heavier chalky soils.
Reproduction: Perennial forte, reproduces by seeds and by new shoots from roots. Capable of reproducing from cut pieces. Flowers almost nine months a year. Many types of dandelions are capable of forming viable seeds without fertilization.
Seed production: Reproductive capacity of one plant is usually 2000 seeds per season.
Seed dispersal: Relatively high potential for long distance dispersal.
Competition: Expansion of lateral roots suppresses growth of vegetation in the area around plant. However, when growing in meadows, where other herbage is tall, dandelions are much less aggressive competitors.
Control: Remains sensitive to application of 2,4-D nearly the entire growing season.
Notes: Dandelion seeds are particularly susceptible to toxic substrate.


Thlapsi arvense L.
Field pennycress, fanweed (Brassicaceae)

Origin: Native to Asia, introduced from Europe.
Known locations in RMNP: Beaver Meadows, Skyland Ranch, roadside 1 mile west-south of Grand Lake.
Geographic distribution: Most troublesome in prairie provinces of Canada and northwestern states. Especially prevalent in northwestern U.S. Found in Colorado from 4000 to 9500'.
Ecological distribution: Weedy species in roadsides, meadows, fields, and other disturbed waste places, almost ubiquitous. Grows in grain fields, along roadsides, grasslands and in waste places. Found in a wide range of climatic conditions. and can be found in both dry and wet habitats.
Soils: Found on a wide range of soils, but common on heavier soils.
Reproduction: Annual or winter annual forte, reproduces by seeds. Species is self-compatible. Flowers May to June. Seeds reach maturity in July.
Seed production: Average seed yield is 2000/plant, but may produce 1600-15,000 seeds/plant. Normal germination is 80%.
Seed longevity: Seeds are known to remain viable in soil up to 6 years.
Seed dispersal: Seeds dispersed mainly by wind. May also be dispersed by water because seeds float. Low potential for dispersal based on seed weight and seed size.
Germination: Germination enhanced with temperatures alterations from 10-25 C, and exposure to light. Most seasonal emergence occurs by mid-May, although many other seedlings may continue to emerge right through the end of the growing season. Most seeds germinate during the first four growing seasons.
Control (chemical): Remains susceptible to 2,4-D applications throughout the year. Also susceptible to MCPA salt, bromoxynil-MCPA-dicamba, 2,4-D mecoprop, linuron-MCPA, and dichlorprop-2,4-D.
Notes: Adds a bad flavor to milk if eaten by cows, presence of seed in flour renders it undesirable. May cause gastric distress in livestock.


Tragopogon dubius Scop. Tragopogon major
Western salsify, yellow salsify (Asteraceae)

Known locations in RMNP: Estes Park, documented in montane uplands.
Assessment: A few scattered populations in RMNP. When added together, all populations would cover an estimated area less than 5 hectares. Found in areas disturbed in the last 11-50 years. Does not appear to be affecting native plant communities or secondary succession processes.
Origin: Introduced from Europe.
Geographic distribution: Relatively widespread throughout U.S.
Ecological distribution: Disturbed sites and in low quality range sites. Fields, roadsides, and waste places, and hot, dry valleys.
Reproduction: Biennial or perennial, reproduces by seeds. Flowers May to July.
Seed longevity: Maximum period of seed dormancy not exceeding one year.
Control: Western salsify is not an aggressive weed, and control is seldom necessary.


Trifolium hybridum L.
Aliske clover (Fabaceae)

Origin: Introduced forb, very similar to red clover.
Known locations in RMNP: Moraine Park, Hollowell Park, Horseshoe Parking Area. Introduced into hay meadows and spreading along trails.
Assessment: An intermediate number of patchy distributed populations. When added together, all populations would cover an estimated area less than 5 hectares. Found in sites disturbed in the last 11-50 years. Plants may delay establishment of native species.
Ecological distribution: Well suited to high mountain land having above average moisture, particularly wetter mountain parks.
Soil: Prefers heavy silt or clay, not adapted to sand. Somewhat more tolerant of acidic soils than red clover. Also adapted to cool temperatures and waterlogged soils.
Reproduction: Perennial forb but only survives through a single winter. Reproduces by seeds.
Seed longevity: Long-lived seeds, some viable seeds after three years burial in sterile soil.
Germination: In laboratory, plant did not readily germinate at 6.7 C after 7 days, but germinated readily when temp. was raised to 25 C.
Control: See Trifolium repens.


Trifolium pratense L.
Red clover, purple clover (Fabaceae)

Origin: Introduced forb.
Assessment: An intermediate number of patchy distributed populations. When added together, all populations would cover an estimated area less than 5 hectares. Found in sites disturbed in the last 11-50 years. Plants may delay establishment of native species.
Known locations in RMNP: Roadside clearings, turf, meadows, along trails. Escaped from cultivation along trails, montane. Lower Black Canyon, Beaver Point.
Ecological distribution: Cultivated forage plant, escaping, but seldom persisting in Utah. Requires mean annual ppt. of 20", well adapted to cut timberlands and moderately acid soils.
Soils: Does well on slightly acid soils (5.8-6.7), production drops off rapidly in acid soils. Loams and silty loams that are well drained.
Reproduction: Short lived perennial forte, reproduces by seeds.
Seed longevity: Seeds may remain dormant up to 3 years. Some viable seeds after 39 years burial in sterile soil.
Germination: Seeds did not germinate at 6.7 C after 7 days, but germinated readily at 25 C.
Control: Resistant to MCPA and 2,4-D amine and ester, moderately resistant to mecoprop salt.


Trifolium repens L.
White clover, Dutch clover (Fabaceae)

Known locations in RMNP: Lower Black Canyon and Cub Lake Trail.
Origin: Native of Eurasia, possibly North America.
Assessment: An intermediate number of patchy distributed populations. When added together, all populations would cover an estimated area less than 5 hectares. Found in sites disturbed in the last 11-50 years. Plants may delay establishment of native species.
Geographic distribution: Newfoundland to Alaska and south to Florida and California, but more abundant in north. Adapted to a wide range of climatic conditions.
Ecological distribution: Cultivated forage and pasture plant. Grasslands, roadsides, open pasture woods, especially in lawns, along trails. meadows.
Soils: No more than slightly acidic soils, does not do well on acidic soils. Scarce on soils with pH below 4.0, but does well on soils with pH from 5.6-7.0. Found in virtually all soil types, but dies if salt concentrations rise above 0.3%. Moderately fine or medium textured, on clay or loam and coarse granite soils.
Reproduction: Perennial herb. reproduces by stolons and seeds. Plant is mostly self-incompatible, and is cross pollinated by insects. In closed systems with continuous grazing or mowing, establishment by seed is rare.
Seed longevity: Long-lived seed, some viability after 30 years burial in sterile soil.
Shade tolerance: Generally restricted to open habitats. Plant is relatively shade intolerant.
Seed production: Produces 525-600 kg seed/ha.
Seed dispersal: Most seed is likely spread incidentally by the movement of livestock (or other animals) and humans.
Germination: No special light or temperature requirements for germination.
Competition: Once established, colonizes bare ground, and may invade disturbed areas in pastures.
Control: T. repens is resistant to MCPA and 2,4 D amine, but is quite sensitive to mecoprop. Dicamba or dicamba mixtures can also be used to control white clover.
Biological: Frequent, intense grazing encourages growth of white clover. Moderate grazing may permit establishment of other species.
Notes: Some people consider white clover to be a troublesome weed in lawns, while others seed it with turf grasses because of its ability to fix nitrogen.
References:

Turkington, R. and J.J. Burdon. 1983. The biology of Canadian weeds. 54. Trifolium 
    repens L. Canadian Journal of Plant Science 63 :243-266.

Triticum aestivum L. Wheat
Triticum sp. Sterile wheatgrass (Poaceae)

Assessment: A few scattered populations of wheat in RMNP. When added together, all populations would cover an estimated area less than 5 hectares. Plants appear to be having little impact on native plant communities and on secondary succession processes.
Known locations in RMNP: This common crop is not believed to be a problem in RMNP.
Ecological distribution: Widely grown and often escaping. Roadsides and along trails. Plants frequently volunteer, surviving for a season along roadsides and trails. Crop prefers cool areas.
Notes: Sterile wheatgrass is used for erosion control, and in restoration projects. Sterile wheatgrass does not produce viable seed.


Verbascum thapsus L.
Woody mullein, velvet dock

Assessment: An intermediate number of patchy distributed populations. When added together, all populations would cover an estimated area of 11-50 hectares. Found in areas with no known disturbance for last 100 years.
Origin: Europe, native of Eurasia.
Geographic distribution: Scattered throughout Colorado from 4500 to 9500', common throughout temperate parts of North America.
Ecological distribution: Open sites, especially along roadsides. Meadows, pastures, waste areas, river bottoms, roadsides. Occurs in areas with mean annual precipitation of 50-150 cm, and the growing season is at least 140 days.
Soils: Common on gravely or stony soils, most abundant in coarse soils with pH of 6.5-7.8.
Reproduction: Biennial forb, reproduces by seeds. Flowering and seed production occur June through August in the second year. Plants can be self-pollinated.
Seed dispersal: Seeds have no specialized mechanism for long distance dispersal. Movement of the stalk by wind or large animal is required to release seeds from parent plant. Seeds are dispersed as far as 11m, but 93% of seeds fall within 5 m of parent.
Seed production: 100,000-180,000 seeds/plant.
Seed longevity: Seeds can remain viable for over 100 years.
Germination: Mullein seeds can germinate under a wide range of environmental conditions. Germination is inhibited below 10 C and at constant temperatures above 40 C. Light also greatly increases germination of seeds.
Competition: Mullein is easily out competed in areas with dense vegetation, but readily grows in disturbed sites. Mullein is likely an early colonist of disturbed sites because seeds remain viable for long periods.
Control: Difficult to control because of the large number of seeds produced per plant
Mechanical: Remove plant mechanically with a spade before flowering is initiated. Mow close to ground, hoe or spade out rosettes below crown in autumn or early spring. Pulling the rosettes before flowering will prevent the deposition of more seeds into the soil (there may still be a large dormant reserve of seeds underground).
Chemical: 2,4-D does little harm to mullein because tiny hairs prevent droplets from touching leaf surface. Adding a surfactant to reduce the surface tension greatly increases toxicity. A single application of 2,4-D/2,4,5 T mixture (at 16 ounces/acre) in June or early September will control mullein.
Notes: Livestock will not eat plant due to wooliness.
References:

Gross, K.L. and P A. Werner. 1978. The biology of Canadian weeds. 28. Verbascum 
    thapsus L. and V. blattaria L. Canadian Journal of Plant Science 58:401-413.

Hoshovsky, M.C. 1988. Element Stewardship Abstract tor Verbascum thapsus. The 
    Nature Conservancy, San Francisco, CA.

Verbena bractenta Laq. and Rodr.
Prostrate vervain

Known locations in RMNP: Found in a few locations in RMNP.
Assessment: An intermediate number of patchy distributed populations. When added together, populations would cover an estimated area less than 5 hectares. Appears to be having little effect on native plant communities or succession processes.
Origin: Native to areas Ohio and westward, and southward. Locally introduced to northeastern states and Pacific Coast.
Geographic distribution: Widespread throughout North America.
Ecological distribution: Fields. roadsides, waste areas, and other disturbed sites.
Reproduction: Annual or perennial, reproduces by seeds. Flowers June to August.
Control: Pull or hoe individual plants.


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