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Aquatic and Wetland Vascular Plants of the Northern Great Plains

63. Poaceae, the Grass Family

19. Panicum L. -- Panic grass

1. Panicum capillare L. -- Common witchgrass

Weedy, tufted annual 1.5-5(7) dm tall, often purplish at the base and in the panicle; culms erect to decumbent and spreading, sometimes sparingly branched below. Leaf blades (2)5-16(27) mm wide, hispid on both surfaces or sometimes mainly on the margins toward the base; sheaths prominently papillose-hispid; ligules a fringe of hairs from a membranous base, 0.5-2.2 mm long. Inflorescence an open, diffuse panicle obovoid to oblong in outline, usually purplish, mostly 0.9-3 dm long (secondary panicles from axils often smaller when present), eventually breaking off the plant to tumble in the wind, the branches and pedicels widely spreading or the lower ones crowded and partly included in the upper leaf sheath, strongly scabrous. Spikelets containing one terminal fertile floret and one sterile floret, disarticulating below the glumes, lanceolate-acuminate in shape; glumes very unequal, the first glume broadly ovate, acute to acuminate, 1-2 mm long, 3- to 5-nerved, sometimes scabrous on the midvein, the second glume ovate-lanceolate, acuminate, 2.5-3.5(4) mm long, 5- to 7-nerved, glabrous or scabrous on the nerves; sterile lemma very similar to the second glume but often a little shorter, lacking a palea; fertile lemma hardened and shiny, elliptic-ovate, 1.5-1.9 mm long, 5- to 7-nerved; palea also hardened, its margins enclosed by the inrolled margins of the lemma; anthers 0.7-1.1 mm long. Grain retained inside the fertile floret. Jul--Sep(Oct). Shores, stream banks, and a variety of disturbed habitats, including roadsides and cropland; very common; (Que. to B.C., s throughout the U.S.; also Bermuda).

P. capillare is a prime example of an opportunistic weed that ventures into wetland habitats only during drawdown. Otherwise, it is better known as an upland weed.

Fall panicum, P. dichotomiflorum Michx., is another weedy annual of moist, disturbed habitats that can sometimes be found on stream banks, alluvial bars, shores and in wet ditches from e SD to e and c NE. It differs from P. capillare in its more robust habit and essentially glabrous foliage, among other characters.

Switchgrass, P. virgatum L., is a well known, dominant tallgrass prairie species that often occupies the mesic zone around basins and bordering streams. It differs from P. capillare in its taller stature and perennial, rhizomatous habit.

Among annual weeds of the Panicum tribe (Paniceae), the foxtails or pigeongrasses, Setaria spp., sometimes invade previously flooded substrates. Like panicums, these have 2-flowered spikelets that disarticulate below the glumes, with the lower floret empty or staminate and the upper one fertile and hardened. The spikelets are borne in distinctive bristly panicles that are condensed, cylindric and spikelike. Most often encountered in drawdown zones is S. glauca (L.) Beauv., yellow foxtail, with yellow-green spikelets 2.5-3.5 mm long, the second glume only 1/2 the spikelet length and sheaths with glabrous margins. S. viridis (L.) Beauv., green foxtail, is much less frequent in wetlands. It has green spikelets mostly less than 2.5 mm long, the second glume as long or nearly as long as the spikelet and sheaths with the upper margins ciliate.

GIF- Species Photo/Drawing

Panicum capillare (from Hitchcock 1950).
GIF- Distribution Map

Map key

Previous Section -- Muhlenbergia richardsonis (Trin.) Rydb. -- Mat muhly
Return to Family -- Poaceae - The Grass Family
Next Section -- Phalaris arundinacea L. -- Reed canarygrass

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