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Poaceae, Aristidoideae, Aristideae - Threeawn

(Family, Subfamily, Tribe)

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Some references still have this tribe under the Subfamily Arundinoideae.


 

        

 

tribe Aristideae

Purple Threeawn Aristida purpurea var. purpurea

Upright bunch grass with drooping tuft of silky purple seed heads (panicles).  Thread-like grass about 12-28" tall.  Leaves very narrow, up to 7" long.  Each fruit has three long hairs (awns) that spread apart at maturity.  Not a good forage for cows or wildlife.

Will crossbreed with A. longiseta and A. roemeriana.

Photos taken in Taylor County, Texas, May 2004, April 2005, June 2007

(Native of Texas - but not of my area)

Base: perennial, no rhizomes, no stolons (runner stem)

Blade (leaf): 3-18cm long, 0.7-2mm wide, basal plus longer on culm

Sheath (leaf part encircling stem): tufts of hair on sides of collars

Culm (main grain stem): drooping, 25-70cm tall

Inflorescence: 10-25cm long, many thin drooping branches

Spikelet: on long pedicels

Glume: second is twice the length of first

Lemma: 10-12mm long to base of awns, twisted above

Awns: Three, 3.5-4.5cm long occasionally up to 6cm long, soft when young, stiff and spreading when dry

Variation

           

 

tribe Aristideae

Red Threeawn (Dogtown Grass) Aristida purpurea var. longiseta (Aristida longiseta)

Photos taken in Taylor County, Texas, July 2007

(Native of Texas - but not of my area)

Base: perennial, no rhizomes, no stolons (runner stem)

Blade (leaf): 8-15cm long,  less than 2mm wide, basal plus longer on culm

Culm (main grain stem): drooping, 10-35 (-50)cm tall

Inflorescence: few thin drooping to erect branches

Spikelet: on long or short pedicels

Glume: first is 1/2-2/3 of second, the second 16-25mm long

Lemma: 13-15mm long to base of awns, straight or slightly twisted above

Awns: Three, 4-10cm long, stout when short, soft when young, stiff and spreading when dry

Variation

Wright Threeawn Aristida purpurea var. wrightii (Aristida wrightii)

Looks like A. purpurea var. fendleriana but does not have basal blade cluster.

13-30 tall, three awns 5/8-1 1/8 long, poor forage value for wildlife and fair to poor grazing quality for livestock.

(Native of Texas - but not of my area)

Base: perennial, no rhizomes, no stolons (runner stem)

Blade (leaf): 10-25cm long, 1-2mm wide, high on culms no basal cluster

Sheath (leaf part encircling stem): tufts of hair on sides and back of collars

Culm (main grain stem): erect, 35-80cm tall, course

Inflorescence: 12-27cm long, very short branches occasionally with a very long stiff lower branch

Spikelet: appressed, on short pedicels, bunched

Glume: broad, first is 1/2-3/4 second, the second 11-15mm long

Lemma: stout, longer than second glume, 5-7mm long to base of awns, equal or slightly longer then second glume

Awns: Three on thick column, 15-30(-40)mm long

Variation

Blue Threeawn (Nealley Threeawn) Aristida purpurea var. nealleyi (Aristida glauca, Aristada nealleyi)

(Native of Texas - Taylor, Runnels, Coke, Brown)

Base: perennial, no rhizomes, no stolons (runner stem)

Blade (leaf): 0.7-1.5mm wide, basal and on culms

Sheath (leaf part encircling stem): tufts of hair on sides of collars

Culm (main grain stem): erect, 15-50cm tall

Inflorescence: 6-18cm long, slender appressed branches

Spikelet: appressed, on short pedicels

Glume: first is 1/2-2/3 second, the second 7-12mm long

Lemma: longer than second glume, 5-7mm long to base of awns

Awns: Three on 1-3mm column, 15-20cm long

 


Other Species In My Area

Oldfield Threeawn (Prairie Threeawn) Aristida oligantha

Long culm with short perpendicular spikelets, two awns twist together, culm zigzags

(Native of Texas - Taylor, Callahan, Eastland, Brown)

Base: annual, no rhizomes, no stolons (runner stem)

Blade (leaf): 10-25cm long,  less than 2mm wide, basal plus shorter on culm

Sheath (leaf part encircling stem): mostly glabrous

Culm (main grain stem): erect, branching, 15-80cm tall

Inflorescence: 5-14cm long, purple-ish, a few widespread branches

Spikelet: on very short pedicels

Glume: nearly equal length, 18-25mm long, second has an awn 1cm or more long extending past Lemma

Lemma: 6-28mm long to base of awns

Awns: Three, 3-7cm long, stiff and spreading when dry

 

Arrowfeather Threeawn Aristida purpurascens

(Native of Texas - but not of my area)

Base: perennial bunchgrass, rhizomes, no stolons (runner stem)

Blade (leaf): 15-30cm or more long, 1-2.5mm wide

Sheath (leaf part encircling stem): mostly glabrous

Culm (main grain stem): erect, 2mm diameter, 35-80cm tall

Inflorescence: 15-35cm long, appears congested on stem

Spikelet: on short pedicels

Glume: first is scabrous 7-12mm long, second shorter

Lemma: purple, 5-7mm long to base of awns

Awns: Three, 5-28cm long, do not twist or spread to horizontal when dry

 

Sixweeks Threeawn Aristida adscensionis

(Native of Texas - but not of my area)

Base: annual, no rhizomes, no stolons (runner stem)

Blade (leaf): short, 1-2.5mm wide

Sheath (leaf part encircling stem): glabrous, much shorter then internodes

Culm (main grain stem): erect and un-branched or reclined with branches that have abrupt bends at nodes, 15-50(10-80)cm tall

Inflorescence: compressed, 6-15(-20)cm long

Spikelet: clustered on widespread very short branches

Glume: first 4-8mm long, second 7-11mm long

Lemma: 6-9mm long to base of awns

Awns: Three, 7-15(-20)cm long with two shorter, stiff and spreading when dry but not horizontal, flattened at base

 


 

Also see:

Texas Grama     Brome

 


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