13.002.   AVENULA (Dumort.) Dumort.

DRAFT TREATMENT. Please send comments to Mary Barkworth.
Gordon C. Tucker

Plants perennial; cespitose, sometimes stoloniferous. Culms 10-110 cm. Sheaths usually open, sometimes closed for most of their length; ligules membranous, acute or truncate; blades flat or folded, adaxial surfaces unribbed, with a furrow on either side of the midveins, margins sclerenchymatous. Inflorescences reduced panicles, many branches (all branches in depauperate specimens) bearing a single spikelet. Spikelets with 2-7 florets; rachillas glabrous on the side adjacent to the paleas, pubescent elsewhere; disarticulation above the glumes and beneath the florets. Glumes as long as or longer than the adjacent lemmas, 1-3-veined; calluses acute; lemmas 5-7-veined, obtuse, bifid, awned from about midlength, awns geniculate, flattened or terete and twisted below the bend; paleas with lateral wings less than 1/2 as wide as the intercostal region, apices shallowly bifid; lodicules 2, entire, unlobed; anthers 3. Caryopses more than twice as long as the hila; endosperm liquid or semi-liquid. x = 7. Name a diminutive of Avena.

Avenula is a genus of approximately 30 species, most of which are European. One species is native to the Flora region, and one has been introduced. The genus is frequently included in Helictotrichon, from which it differs in having acute cauline ligules, unribbed leaves, rachillas glabrous on one side, unlobed lodicules, short hila, liquid to semi-liquid endosperm, and no sclerenchyma ring in its roots.


SELECTED REFERENCES Dixon, J.M. 1991. Biological flora of the British Isles: Avenula (Dumort.) Dumort. J. Ecol. 79:829-865; Gervais, C. 1973. Contribution à l'étude cytologique et taxonomique des avoines vivaces (e.g. Helictotrichon Bess. et Avenochloa Holub). Denkschr. Schweiz. Naturf. Ges. 88:3-166; Holub, J. 1963. Ein Beitragzur Abgrenzung der Gattungen in der Tribus Aveneae: die Gattung Avenochloa Holub. Acta Horti Bot. Prague 1962:75-86.

1
Sheaths closed for less than 1/3 of their length, sheaths and blades smooth to scabridulous; panicles 4-13 cm long, mostly 0.8-2.5 cm wide; awns 10-17 mm long, flattened below the bend ..... 1. A. hookeri
Sheaths closed to near their top, sheaths and blades usually pubescent; panicles 6-20 cm long, 2-6 cm wide; awns 12-26 mm long, terete below the bend ..... 2. A. pubescens


1.   Avenula hookeri (Scribn.) Holub
Spike Oatgrass

Plants cespitose, not stoloniferous. Culms 10-75 cm, erect. Sheaths closed for less than 1/3 of their length, smooth to scabridulous; ligules 3-7 mm, acute, usually lacerate; blades mostly 4-20 cm long, 1-4.5 mm wide, smooth to scabridulous, margins cartilaginous and whitish. Panicles (4)6-11(13) cm long, mostly 0.8-2.5 cm wide, erect or ascending; branches 10-25 mm, usually straight, stiff, mostly with 1-2 spikelets. Spikelets 12-16 mm, with 3-6 florets; rachilla internodes mostly 1.5-2.5 mm, hairs 0.2-1.5 mm. Glumes thin, acute; lower glumes 9-13 mm, 3-veined; upper glumes 9-14 mm, 3-5-veined; calluses bearded, hairs usually shorter than 1 mm; lemmas 10-12 mm, awned, awns 10-17 mm, flattened below the bend; paleas 6-8.75 mm; anthers 2.5-5 mm. 2n = 14.

Avenula hookeri grows on mesic to dry, open prairie slopes, hillsides, forest openings, and meadows, in montane to subalpine zones, from Alaska and northern Canada to New Mexico.


2.   Avenula pubescens (Huds.) Dumort.
Downy Alpine Oatgrass

Plants shortly stoloniferous. Culms 30-110 cm, erect or geniculate at the base. Basal leaves: sheaths closed to near the top; ligules 0.5-1 mm, truncate; blades 10-40 cm long, 2-6(8.5) mm wide, usually with hairs to 2 mm. Cauline leaves: sheaths closed for nearly their entire length, pubescent; ligules 5-8 mm, acute; blades 10-40 cm long, 2-6 mm wide, usually pubescent, margins very narrowly cartilaginous. Panicles 6-20 cm long, 2-6 cm wide, erect or nodding; branches 4-35 mm, flexuous or straight, with 1-4 spikelets. Spikelets 10-26 mm, with 2-4 florets; rachilla internodes about 2.5 mm, hairs 3-7 mm. Glumes scabrous on the veins. Lower glumes 7-20 mm, 1(3)-veined; upper glumes 10-26 mm, 3-veined; calluses bearded, hairs 2-5 mm; lemmas 8-16 mm, awned, awns 12-26 mm, terete below the bend; paleas 8-12 mm; anthers 5-7 mm. 2n = 14, 28.

Avenula pubescens is native to Eurasia, where it grows in meadows, pastures, and woodland clearings. The most widespread taxon is Avenula pubescens (Huds.) Dumort. subsp. pubescens, which differs from Avenula pubescens subsp. laevigata (Schur) Holub in having smaller spikelets (10-17 mm long with 2-3 florets, versus 15-26 mm long with 3-4 florets). It has been collected in southern Ontario, Ile d'Anticosti in Quebec, and in New England, but is not known to be established in Canada.