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Aquatic and Wetland Vascular Plants of the Northern Great Plains

Key to Taxa of Aquatic and Wetland Vascular Plants


Lead Characteristic Go To
1 Plants small and flattened, less than 3 cm across, free-floating at or beneath the water surface, often not differentiated into stems and leaves; fine roots often produced on the underside of the plants. Lead 2
1 Plants not greatly reduced in size, with stems and leaves, exhibiting various habits but usually anchored in the substrate; roots usually produced. Lead 3
2 Plants with tiny, overlapping, scalelike leaves in 2 rows on branched, filiform stems. SALVINIACEAE (Azolla mexicana)
2 Plants lacking differentiated leaves and stems. LEMNACEAE
3 Plants nonflowering, reproducing by spores (ferns and fern allies). Lead 4
3 Plants producing flowers, although these not always conspicuous (flowering plants). Lead 9
4 Stems jointed, longitudinally ridged, simple or with whorled branches; leaves scalelike, fused to form a toothed sheath at each joint of the stem; sporangia borne in terminal cones. EQUISETACEAE (Equisetum)
4 Stems not jointed, often subterranean; leaves not scalelike, often with expanded, simple or compound blades; sporangia not borne in cones. Lead 5
5 Leaves narrow and grasslike, lacking an expanded blade. Lead 6
5 Leaves with an expanded, simple or compound blade. Lead 7
6 Leaves arising from a cormlike base; sporangia contained in swollen leaf bases. ISOETACEAE (Isoetes melanopoda)
6 Leaves arising from filiform rhizomes; sporangia contained in round, hardened sporocarps borne on branches from the rhizomes. MARSILEACEAE (See Pilularia americana as described under Marsilea vestita)
7 Leaves 4-foliate, appearing like a 4-leaved clover. MARSILEACEAE (Marsilea vestita)
7 Leaves simple or pinnately lobed to compound. Lead 8
8 Leaf blades simple, entire, subtending a spike of sporangia. OPHIOGLOSSACEAE (Ophioglossum vulgatum)
8 Leaf blades pinnatifid to pinnately compound; sporangia grouped in sori on modified or unmodified leaves. POLYPODIACEAE
9 Trees and shrubs. Lead 10
9 Herbs, woody only at the base if at all. Lead 16
10 Shrub with pinnately compound leaves. FABACEAE (Amorpha fruticosa)
10 Trees or shrubs with simple leaves. Lead 11
11 Leaves scalelike, 1-5 mm long. TAMARICACEAE (Tamarix ramosissima)
11 Leaves not scalelike, all or mostly longer than 5 mm. Lead 12
12 Trees or shrubs with nonshowy, unisexual flowers in catkins. Lead 13
12 Shrubs with greenish, white or yellow flowers, these perfect and not in catkins. Lead 14
13 Dioecious trees and shrubs with male and female catkins on separate plants; female catkins bearing capsules, these maturing to release cottony seeds. SALICACEAE
13 Monoecious shrubs with male and female catkins on the same plant; female catkins bearing winged nutlets. BETULACEAE
14 Leaves opposite. CORNACEAE (Cornus stolonifera)
14 Leaves alternate. Lead 15
15 Leaves palmately lobed and veined; fruit a berry. GROSSULARIACEAE (Ribes)
15 Leaves finely toothed, pinnately veined; fruit of 5 (or fewer) follicles. ROSACEAE (Spiraea alba)
16 Flowers much reduced in size, (2) several to many crowded into involucrate heads and sharing a disklike receptacle; each head resembling a single flower; flowers of the head usually of 2 types, with petaloid ray flowers around the outside and less conspicuous disk flowers in the central portion of the head, or the heads often comprised entirely of ray or disk flowers; involucral bracts herbaceous to membranous, green or sometimes colored, in 1 to many series surrounding the disk, sometimes spiny-tipped and united. ASTERACEAE
16 Flowers sometimes small in size but not crowded into involucrate heads and not appearing as ray and/or disk flowers. Lead 17
17 Submersed leaves present, finely divided into few to many, filamentous or flat, narrow segments. Lead 18
17 Submersed leaves, if present, entire, toothed or incised but not finely divided into segments. Lead 22
18 Submersed plants with small bladders (1-4 mm in diameter) on filiform segments of finely dissected leaves; flowers irregular and spurred, yellow, in scapose racemes held above the water surface. LENTIBULARIACEAE (Utricularia)
18 Submersed or emergent plants lacking bladders; flowers regular, colored or greenish, not spurred; inflorescence other than a raceme. Lead 19
19 Submersed leaves long-petioled, pinnately compound, with the leaflets variously divided into flat, narrow segments; stems and petioles mostly over 5 mm thick, conspicuously hollow and chambered. APIACEAE (submersed form of Sium suave)
19 Submersed leaves sessile, or if petioled, then palmately divided; stems less than 5 mm thick. Lead 20
20 Leaves whorled or mostly so; flowers greenish and nonshowy. Lead 21
20 Leaves alternate; flowers white or yellow. RANUNCULACEAE (Ranunculus)
21 Leaves dichotomously branched, the segments spinulose. CERATOPHYLLACEAE (Ceratophyllum demersum)
21 Leaves pinnately branched, lacking spinulose projections. HALORAGACEAE (Myriophyllum)
22 Leaves all submersed or some floating also, all basal or borne on stems which are limp when removed from water and usually prostrate when stranded. Lead 23
22 Leaves mostly or all emersed (or mostly large and floating in Nymphaeaceae), borne on erect to procumbent, aerial or partly submersed stems, or the leaves basal; leaves sometimes apparently lacking. Lead 34
23 Leaves all basal. Lead 24
23 Leaves borne on elongate stems. Lead 26
24 Submersed leaves with a median band containing many fine longitudinal veins, the median band bordered by narrow, nerveless or sparsely nerved margins; floating leaf blades none; plants dioecious, producing either oblong female flowers that float on the water surface attached to a long peduncle or producing many tiny male flowers that are released free-floating from a spathe at the plant base. HYDROCHARITACEAE (Vallisneria americana)
24 Submersed leaves lacking a prominent median band of veins, the few to several principal longitudinal veins evenly distributed on both sides of the midvein, often obscure; floating leaves sometimes produced; plants monoecious or hermaphroditic, although flowers often missing in sterile submersed forms. Lead 25
25 Inflorescence a submersed panicle with whorled branches. ALISMATACEAE (submersed form of Alisma gramineum)
25 Inflorescence absent; plants apparently sterile .... Several taxa of monocots that are normally emergent will produce sterile submersed forms during juvenile stages when inundated. Some common examples include Sagittaria spp. and Alisma plantago-aquatica, both of which produce rosettes of brittle, dark green, sword-shaped leaves, often along with long-petioled floating leaves. The floating blades are generally sagittate (Sagittaria) or oblong-lanceolate (Alisma) in shape. (Of our Alismataceae only Alisma gramineum appears capable of flowering and fruiting underwater and it does so frequently.) Typha spp., Sparganium spp. and some grasses, e.g. Zizania aquatica and Glyceria spp., have sterile submersed forms featuring few to several flexuous, light green, tapelike leaves arising from the base. None of these sterile forms can be confidently identified to species unless one can relate them to more mature examples at the same site or can observe their development through the growing season.  
26 Leaves all or mostly alternate, sometimes the uppermost opposite. Lead 27
26 Leaves all opposite or whorled. Lead 30
27 Leaves linear, 2-10(15) cm long, 2-5(7) mm wide, the midvein inconspicuous; flowers pale yellow, solitary in the upper axils; fruit a many-seeded capsule. PONTEDERIACEAE (Zosterella dubia)
27 Leaves of various shapes and sizes, but if fitting the above dimensions, then the midvein prominent; flowers in various types of inflorescences; fruit hard, one-seeded. Lead 28
28 Flowers pink, in dense, terminal, spikelike racemes. POLYGONACEAE (Polygonum amphibium)
28 Flowers greenish, nonshowy, in terminal or axillary spikes. Lead 29
29 Leaves all submersed, filiform, ca. 0.5 mm wide; flowers enclosed in leaf sheaths at anthesis, the peduncles elongating and often coiling as fruits develop; mature fruits borne in an umbel. RUPPIACEAE (Ruppia maritima)
29 Leaves all submersed or some floating, variously shaped; flowers and fruits borne in elongate to short spikes. POTAMOGETONACEAE (Potamogeton)
30 Leaves in whorls of 3 or mostly decussate; flowers axillary and extended to the water surface by a long, threadlike hypanthium. HYDROCHARITACEAE (Elodea)
30 Leaves opposite (most obviously the uncrowded lower leaves); flowers completely contained in the leaf axils. Lead 31
31 Leaf blades abruptly broadened at the base and sheathing the stem; fruits fusiform, only 1 per node. NAJADACEAE (Najas)
31 Leaf blades of about equal width throughout, only weakly clasping the stem if at all; fruits crescent-shaped or round. Lead 32
32 Fruits mostly 2-4 per node, crescent-shaped with a persistent style. ZANNICHELLIACEAE (Zannichellia palustris)
32 Fruits 1 or 2 per node, round; styles deciduous. Lead 33
33 Small, densely branched plants usually sprawling on mud and rooting at the nodes; fruit a capsule containing numerous minute, ridged seeds. ELATINACEAE (Elatine triandra)
33 Irregularly branched plants, normally submersed, the upper leaves sometimes floating; fruit orbicular, cleft down the middle and eventually splitting into 4 nutlets. CALLITRICHACEAE (Callitriche)
34 Plants grasslike, rushlike or reedlike, emergent or terrestrial; leaves long, linear and parallel-veined, often sheathing at the base, or leaf-blades absent, the leaves reduced to sheathing around the base of the stem. Lead 35
34 Plants not grasslike, rushlike or reedlike; leaves of various shapes, net or parallel-veined, seldom sheathing at the base; all or most of the leaves with blades. Lead 45
35 Individual flowers showy, yellow, pink or white to blue-violet. Lead 36
35 Individual flowers not showy, usually greenish to brownish. Lead 38
36 Plants tall, rushlike, with large pink flowers in a terminal umbel.
BUTOMACEAE (Butomus umbellatus)
36 Plants low, rather grasslike, with yellow or white to blue-violet flowers. Lead 37
37 Flowers usually blue-violet (white), in clusters subtended by a 2-bracted spathe. IRIDACEAE (Sisyrinchium montanum)
37 Flowers yellow, not subtended by a spathe. LILIACEAE (Hypoxis hirsuta)
38 Typically emergent marsh plants with broad (mostly 5 mm or more wide), long, linear leaves; flowers unisexual, arranged in a terminal spike or in globose heads, the male flowers borne above the female. Lead 39
38 Plants of various habits; flowers perfect or imperfect, when imperfect, the male and female flowers contained in small spikes of grasslike plants. Lead 40
39 Flowers in a dense, terminal spike of 2 portions, the upper part male and the lower female; plants usually 1 m or more tall; cattails. TYPHACEAE (Typha)
39 Flowers in few to many dense, globose heads, the upper heads male and the lower female; plants 1 m or less tall; burreeds. SPARGANIACEAE (Sparganium)
40 Inflorescence a dense, cylindric spadix 5-10 cm long, protruding laterally from the base of a leaflike extension of the scape; fresh foliage sweetly fragrant when crushed. ARACEAE (Acorus calamus)
40 Inflorescence of various types, but if spicate, then the flowers borne in 1 or more terminal spikes, or if single and lateral, then the spike much less than 5 cm long; foliage not sweetly fragrant. Lead 41
41 Inflorescence a long, slender, spikelike raceme of many flowers; leaves all basal, terete; fruit splitting lengthwise into 3 or 6, one-seeded segments. JUNCAGINACEAE (Triglochin)
41 Inflorescence of various types; leaves seldom all basal, usually some cauline, or leaves apparently reduced to basal sheaths; leaf blades usually flat when present; fruit an achene, grain, capsule, or a group of follicles. Lead 42
42 Perianth segments evident, consisting of 6 tepals; fruit a capsule or 3 (rarely to 6) follicles. Lead 43
42 Perianth absent or reduced to scales or bristles, the flowers enclosed by 1 or 2 chaffy bracts; fruit an achene or grain. Lead 44
43 Flowers usually numerous in dense clusters or loosely flowered cymes; tepals stiff, chaffy; carpels united, the ovary maturing as a 3-valved, many-seeded capsule; widespread plants. JUNCACEAE (Juncus)
43 Flowers few to several in a bracteate raceme; tepals soft, not chaffy; carpels separate or nearly so to the base, each of the 3(to 6) maturing as a 1 or 2(several) seeded follicle; rare bog plant. SCHEUCHZERIACEAE (Scheuchzeria palustris)
44 Leaves in 3 vertical ranks on an often trigonous, solid or pithy stem, or leaves reduced to basal sheaths only; leaf sheaths closed around the stem, sometimes splitting with age; flowers each borne in the axil of a scalelike bract and often with several inner subtending scales or bristles; ovary sometimes contained in a saclike covering (perigynium); fruit a beaked achene; styles bifid or trifid; sedges. CYPERACEAE
44 Leaves in 2 vertical ranks on a terete, usually hollow stem with swollen nodes; leaf sheaths commonly open longitudinally with overlapping margins; flowers each subtended by 2 bracts (lemma and palea) and also by 2 inner, obscure scales (lodicules); ovary never enclosed in a sac; fruit a grain; styles bifid; grasses. POACEAE
45 Broader-leaved monocots; leaves usually curved-parallel veined, sometimes net-veined; perianth parts in multiples of 3 (sometimes obscured by fusion and modification in the ORCHIDACEAE). Lead 46
45 Dicots; leaves net-veined; perianth segments usually in multiples of 4 or 5. Lead 50
46 Leaves petiolate. Lead 47
46 Leaves sessile, sometimes sheathing the stem. Lead 49
47 Leaf blades broadly heart-shaped, about as wide as long; inflorescence a short-cylindric spadix subtended by a broadly ovate spathe. ARACEAE (Calla palustris)
47 Leaf blades elliptic, lanceolate, ovate or sagittate; inflorescence other than a spadix. Lead 48
48 Flowers in a panicle or branched raceme, perfect or imperfect; ovaries many per flower, superior, maturing as flattened achenes. ALISMATACEAE
48 Flowers solitary from a narrow spathe, perfect; ovary 1, inferior, maturing as a many-seeded capsule. PONTEDERIACEAE (Heteranthera limosa)
49 Leaves opposite or some whorled above; flowers regular, reddish-orange with dark spots (rarely solid yellow). LILIACEAE (Lilium philadelphicum)
49 Leaves alternate or mainly basal; flowers irregular, variously colored. ORCHIDACEAE
50 Leaf blades large and leathery, floating or emergent, oblong to oval or round, with a narrow sinus behind the petiole attachment to the blade, (1)1.5-4 dm long or across; stem a thick, fleshy rhizome buried in the mud; flowers large, 4-15 cm across; water lilies. NYMPHAEACEAE
50 Leaves smaller and variously shaped; flowers generally smaller. Lead 51
51 Small insectivorous bog plant; leaves all basal, the blades rotund, mostly less than 1 cm across, the upper surface covered with reddish, sticky glandular hairs that serve to trap insects. DROSERACEAE (Drosera rotundifolia)
51 Plants not insectivorous; leaves not specialized to trap insects. Lead 52
52 Leaves whorled, with 4-12 at each node, the members of each whorl of equal size. Lead 53
52 Leaves opposite, alternate or basal, sometimes both opposite and alternate, or if appearing whorled, then the leaves at each node of differing sizes. Lead 54
53 Stems weak, ascending to reclining, branched; leaves in whorls of 4-6. RUBIACEAE (Galium)
53 Stems erect, simple; leaves in whorls of 6-12. HIPPURIDACEAE (Hippuris vulgaris)
54 Plants low, succulent, the stems often brittle, green to often strongly red; leaves opposite, small and scalelike; flowers embedded in terminal portions of the fleshy stems. CHENOPODIACEAE (Salicornia rubra)
54 Plants without the above combination of characters. Lead 55
55 Perianth consisting of a calyx only, the sepals green or often colored and petaloid, sometimes rudimentary; flowers hypogynous. Lead 56
55 Perianth consisting of both a calyx and corolla, or if the perianth is of only one series, then the flowers epigynous; flowers hypogynous to epigynous. Lead 64
56 Leaves opposite or mostly so. Lead 57
56 Leaves alternate or mostly basal (all basal except for leaflike involucres subtending the flowers in Anemone canadensis, RANUNCULACEAE). Lead 59
57 Flowers in terminal inflorescences. CARYOPHYLLACEAE (Cerastium)
57 Flowers solitary in the axils or in axillary clusters. Lead 58
58 Flowers white to pinkish, solitary in the axils. PRIMULACEAE (Glaux maritima)
58 Flowers greenish, clustered in axillary inflorescences. URTICACEAE
59 Flowers large and showy, white or yellow, 2-5 cm across. RANUNCULACEAE
59 Flowers individually small, white, pink or greenish. Lead 60
60 Leaves all basal; sepals spurred at the base; pistils many on an elongate receptacle. RANUNCULACEAE (Myosurus minimus)
60 Leaves cauline or partly so; sepals not spurred; pistils 5, 6, 1 or none. Lead 61
61 Leaves serrate; pistils 5, fused in a star-shaped ring. SAXIFRAGACEAE (Penthorum sedoides)
61 Leaves entire, undulate or lobed; pistil 1 or none. Lead 62
62 Stems sheathed at the nodes by a membranous ocrea; perianth petaloid or green to brown and winged. POLYGONACEAE
62 Stems without ocreae; perianth green, minute and inconspicuous. Lead 63
63 Flowers perfect. CHENOPODIACEAE
63 Flowers imperfect. AMARANTHACEAE (Amaranthus)
64 Flowers pouchlike and spurred, yellow to orange-yellow, often reddish-brown spotted. BALSAMINACEAE (Impatiens)
64 Flowers not pouchlike, variously colored. Lead 65
65 Inflorescence a simple or compound umbel. Lead 66
65 Inflorescence other than an umbel. Lead 68
66 Leaves simple; flowers deeply pink to red or lilac. Lead 67
66 Leaves compound; flowers white. APIACEAE
67 Leaves all basal, strongly whitened beneath. PRIMULACEAE (Primula incana)
67 Leaves opposite, not whitened beneath. ASCLEPIADACEAE (Asclepias incarnata)
68 Stamens more than 10, or if as few as 9, then the stamens united below into 3 fascicles. Lead 69
68 Stamens 10 or fewer, sometimes united below but not in 3 fascicles. Lead 71
69 Leaves opposite. CLUSIACEAE
69 Leaves alternate or all basal. Lead 70
70 Flowers hypogynous, the sepals, petals and stamens attached to the receptacle directly beneath the gynoecium. RANUNCULACEAE (Ranunculus)
70 Flowers perigynous, the sepals, petals and stamens attached around the rim of a saucerlike or disklike hypanthium. ROSACEAE
71 Leaves pinnately compound, with 3 or more distinct leaflets. Lead 72
71 Leaves simple or sometimes pinnately lobed, not divided into distinct leaflets. Lead 73
72 Leaves once-pinnate; flowers (or fruits) in simple or branched racemes. FABACEAE
72 Leaves twice-pinnate; flowers (or fruits) in dense globose clusters. MIMOSACEAE (Desmanthus)
73 Petals separate or lacking. Lead 74
73 Petals united, at least toward the base. Lead 82
74 Petals present, mainly purple or blue-violet, sometimes white toward the base (actually pink but often drying purple in Epilobium, ONAGRACEAE). Lead 75
74 Petals present or lacking, white, pink or yellow when present. Lead 77
75 Plants acaulescent, the leaves and flowers arising from the base. VIOLACEAE (Viola nephrophylla)
75 Plants caulescent, the leaves and flowers borne on a stem. Lead 76
76 Ovary inferior, elongate to linear, appearing like a pedicel of the flower; seeds often with a coma. ONAGRACEAE
76 Ovary superior, ovoid to globose, enclosed by the tubular calyx; seeds lacking a coma. LYTHRACEAE
77 Sepals 5; petals 5. Lead 78
77 Sepals 4; petals 4 or none. Lead 80
78 Leaves all basal, or one leaf sessile above on each flowering scape and the rest basal. SAXIFRAGACEAE
78 Leaves opposite. Lead 79
79 Leaves glandular-serrate. ELATINACEAE (Bergia texana)
79 Leaves entire. CARYOPHYLLACEAE
80 Ovary superior, sometimes contained in a calyx cup but free of it. Lead 81
80 Ovary inferior. ONAGRACEAE
81 Leaves alternate, usually shallowly to deeply lobed or compound. BRASSICACEAE
81 Leaves opposite, entire. LYTHRACEAE
82 Leaves basal. Lead 83
82 Leaves cauline. Lead 85
83 Leaves simple. Lead 84
83 Leaves trifoliate. MENYANTHACEAE (Menyanthes trifoliata)
84 Flowers in a spike. PLANTAGINACEAE (Plantago)
84 Flowers solitary on peduncles arising from the plant base. SCROPHULARIACEAE (Limosella aquatica)
85 Stamens numbering the same as the corolla lobes. Lead 86
85 Stamens numbering fewer than the corolla lobes. Lead 90
86 Leaves opposite (sometimes appearing whorled because of leaf fascicles in axils). Lead 87
86 Leaves alternate or mostly so. Lead 89
87 Flowers yellow. PRIMULACEAE (Lysimachia)
87 Flowers not yellow. Lead 88
88 Flowers white or greenish-white, less than 5 mm long; fruit 1 or 2 slender follicles; plants with milky juice. APOCYNACEAE (Apocynum cannabinum)
88 Flowers purple (drying dark blue), rarely white, 15 mm or more long; fruit a 2-valved capsule; plants with clear juice. GENTIANACEAE
89 Ovary superior, 4-lobed, splitting into 4 nutlets at maturity; flowers in scorpioid spikes or racemes. BORAGINACEAE
89 Ovary inferior, or partly so, not lobed, maturing as a capsule; flowers in bracteate racemes or solitary in the upper axils. CAMPANULACEAE
90 Flowers blue-violet, slightly bilabiate, in dense terminal spikes. VERBENACEAE (Verbena hastata)
90 Flowers of various colors, but when in terminal spikes, the flowers usually pink or yellow, or if blue-violet, then strongly bilabiate. Lead 91
91 Flowers in capitate or short-cylindric spikes that are peduncled from the axils. VERBENACEAE (Lippia lanceolata)
91 Flowers in racemes, spikes, axillary clusters or solitary in the axils. Lead 92
92 Ovary 4-lobed, splitting into 4 nutlets at maturity; stems 4-angled. LAMIACEAE
92 Ovary not lobed, maturing into a 2-valved capsule; stems usually terete. SCROPHULARIACEAE

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