Three-awn

Three-awn

Taxobox
name = Three-awns


image_width = 240px
image_caption = Purple Three-awn, "Aristida purpurea"
regnum = Plantae
phylum = Magnoliophyta
classis = Liliopsida
ordo = Poales
familia = Poaceae
subfamilia = Arundinoideae
tribus = Aristideae
genus = "Aristida"
genus_authority = L.
subdivision_ranks = Species
subdivision =About 300, see text

The three-awns are the grass genus "Aristida", distinguished by having three awns (bristles) on each lemma of each floret. The genus includes about 300 species, found worldwide, often in arid warm regions. This genus is among those colloquially called "wiregrasses", "speargrasses" or "needlegrasses".

"Aristida" stems are ascending to erect, with both basal and cauline leaves. The leaves may be flat or inrolled, and the basal leaves may be tufted. The inflorescences may be either panicle-like or raceme-like, with spiky branches. The glumes of a spikelet are narrow lanceolate, usually without any awns, while the lemmas are hard, three-veined, and have the three awns near the tip. The awns may be quite long; in "A. purpurea " var. "longiseta" they may be up to 10 cm.

They are characteristic of semiarid grassland. The Wiregrass Region of North America is named for "A. stricta". Other locales where this genus is an important component of the ecosystem include the Carolina Bays, the sandhills of the Carolinas and elsewhere, Mulga scrub in Australia, and the xeric grasslands around Lake Turkana in Africa.

On the other hand, a local increase of the amount of "wiregrass" - which is not well-liked by livestock - is a good indicator of overgrazing.

Selected species

* "Aristida adscensionis" L.
* "Aristida anaclasta"
* "Aristida basiramea" – Fork-tipped Three-awn, Forked Three-awn
* "Aristida behriana" F.Muell.
* "Aristida beyrichiana"
* "Aristida burkei" – "bohlanya-ba-pere" (Sesotho: "horse-madness grass")
* "Aristida californica"
* "Aristida calycina" R.Br.
* "Aristida chaseae"
* "Aristida contorta" F.Muell.
* "Aristida dichotoma" Michx. – Shinner's Three-awn, "poverty grass"
* "Aristida divaricata"
* "Aristida granitica"
* "Aristida guayllabambensis"
* "Aristida hygrometrica" R.Br.
* "Aristida longespica" – Slim-spiked Three-awn
** "Aristida longespica" var. "geniculata" – Red Three-awn
** "Aristida longespica" var. "longespica"
* "Aristida mutabilis"
* "Aristida oligantha" Michx. – Prairie Three-awn
* "Aristida pallens" Cav.
* "Aristida portoricensis" – "Pelos del diablo"
* "Aristida pungens" – Drinn
* "Aristida purpurascens" Poiret – Arrowfeather Three-awn, Purple Needlegrass
* "Aristida purpurea" – Purple Three-awn
** "Aristida purpurea " var. "longiseta"
* "Aristida ramosa" R.Br.
* "Aristida refracta"
* "Aristida spiciformis"
* "Aristida stricta" – Pineland Three-awn, "wiregrass"
* "Aristida suringarii"
* "Aristida swartziana"
* "Aristida tenuifolia"
* "Aristida vagans"
* "Aristida vaginata"

ee also

* New Mexico State University Botanical Garden has a large collection of local "Aristida" species
* "Puccinia aristidae", a plant pathogenic urediniomycete fungus first described from three-awn grass

References

* (1993): "The Jepson Manual - Higher Plants of California": 1234-1235.


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Look at other dictionaries:

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  • three-awn grass — noun see three awn …   Useful english dictionary

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  • red three-awn — noun : a needlegrass (Aristida longiseta) …   Useful english dictionary

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