Aquatic and Wetland Vascular Plants of the Northern Great Plains
63. Poaceae, the Grass Family
1. Agropyron Gaertn. -- Wheatgrass1. Agropyron repens (L.) Beauv. -- Quackgrass
Strongly rhizomatous and weedy perennial, the foliage deep green to somewhat glaucous; culms erect to decumbent, 5-10 dm tall, smooth and hollow. Leaf blades flat to seldom involute, 2-9(14) mm wide, glabrous or pilose on the upper surface; sheaths glabrous or sparsely pilose near the summit, usually with prominent, clawlike auricles at the mouth; ligule very short and membranous, to 0.5 mm long, finely erose. Inflorescence a balanced, bilateral spike 5-19(26) cm long, continuous or somewhat interrupted in the lower portion; rachis joints flattened, scabrous on the angles. Spikelets 1 per node, 3- to 8-flowered, 10-20 mm long; glumes subequal, the first usually slightly shorter than the second, lanceolate, 5-13 mm long, strongly 5- to 7-nerved, firm, glabrous or scaberulous on the midnerve, acute or often awned from a minutely bifid apex, the awn sometimes to 7 mm long; lemmas 7-10(12) mm long, reduced upward, faintly 5-nerved, glabrous, acute or awned like the glumes; palea about equaling the body of the lemma, scaberulous on the margin; anthers prominent, 3-5.5 mm long. Grain brown, oblong-cylindric, 4-5 mm long, remaining enclosed by the firm-textured lemma and palea. Jun--Sep. Wet meadows, ditches, stream banks and other wet or moist places; common; (Intro. from Eurasia and established from Newf. to AK, s to NC, KY, KS and CA).
A few other members of the wheat tribe (Triticeae) are occasionally encountered in wetland habitats, although not to the extent of Agropyron repens and Hordeum jubatum. Among the wheatgrasses, these include A. smithii Rydb. and A. trachycaulum (Link) Malte, the latter including A. subsecundum (Link) A. S. Hitchc. and sometimes itself included in Old World A. caninum (L.) Beauv. A. smithii, western wheatgrass, is well known as a dominant species in native mixed grass prairie and is seldom thought of as inhabiting wetlands; however, some ecotypes do favor alkaline wet meadows in the central and western parts of the Dakotas. The species has even been observed as a codominant emergent in shallow marshes with Eleocharis macrostachya. A. smithii resembles A. repens in general habit but differs markedly in its strongly glaucous color, narrower, often involute leaves and the glumes and lemmas tapered (not bifid) to an awned tip.
A. trachycaulum, slender wheatgrass, occasionally occurs on or near shores and stream banks. Unlike the 2 species already discussed, A. trachycaulum is a bunchgrass lacking rhizomes. Occurring in the northern Great Plains are var. trachycaulum, with lemmas awnless or with awns to 6 mm long, and var. unilaterale (Cassidy) Malte, with lemmas having awns 17-40 mm long.
A. trachycaulum and Hordeum jubatum are often implicated as parents in the formation of the sterile F1 hybrid X Agrohordeum macounii (Vasey) Lepage (formerly Elymus macounii Vasey). The plant resembles the genus Elymus in having 2 spikelets per node on the rachis, and it is similar to Hordeum jubatum in having the rachis disarticulate at maturity. Its hybrid nature is plainly evident by the empty florets. The plant is occasional in moist disturbed habitats such as shorelines and stream banks.
Finally, Elymus canadensis L., Canada wildrye, is a common, tall, tufted perennial of woodlands, moist prairie and road ditches. It is also a frequent inhabitant of stream banks, elevated shorelines and marsh borders. The large, thick, nodding spikes with long, ultimately recurved awns are distinctive for this species in our area.
Agropyron repens (from Hitchcock 1950). |
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