Threeawns
What are they?
Threeawn grasses are most typically found in arid and semi-arid areas, often becoming dominant in desert-like conditions. As such, they are more common and more diverse much further west in the USA than in New Jersey. A small handful of species reach Cape May but most are not particularly common.
Where are they found?
As mentioned above, these are grasses of arid often almost sterile growing conditions and may be found in open areas of disturbed ground, especially where nutrient-poor subsoil has been brought to the surface, such as around gravel workings and other industrial sites.
Identification
Most species of threeawn are rather small and easily-overlooked species, characterized by their long, usually bent or twisted, flower awns. For species recognition, see the individual species comments.
Prairie Threeawn Aristida oligantha
A small grass of dry, semi-arid ground. Flowers July to October. Flowers arranged in a raceme (arranged singly on a common stalk) with three long awns, more or less equal in length.
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Slim-spiked Threeawn Aristida longespica
A small grass of dry, ground, sometimes found in dense stands. Flowers August to October.
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Arrow-feather Threeawn Aristida purpurascens
A small grass of dry, semi-arid ground. Flowers August to October. Flowers arranged in a raceme (arranged singly on a common stalk) with three long awns, more or less equal in length. Very similar to Prairie Threeawn, but a perennial species forming small clumps and with glumes (lowest scales in the flowerhead) being one-veined, not three- or five-veined.
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