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nodding false oat, nodding oatgrass, nodding trisetum

narrow false oat, narrow oatgrass, spike false oat, spike trisetum, trisete a epi

Habit Plants perennial, with both fertile and sterile shoots; cespitose, not rhizomatous. Plants perennial, with both fertile and sterile shoots; cespitose, not rhizomatous.
Culms

(30)50-110 cm, clumped, erect, glabrous or pubescent.

10-120 cm, clumped, erect, usually glabrous, sometimes villous, sometimes scabridulous.

Leaves

2-3 per culm;

sheaths scabridulous or pilose;

ligules 1.5-3 mm, truncate, erose to lacerate;

blades (8.5)15-20+ cm long, (3)7-12 mm wide, flat, ascending, lax at maturity, often scabridulous.

mostly basal or evenly distributed;

sheaths variously pubescent or glabrous;

ligules 0.5-4 mm, truncate or rounded;

blades (3)10-20(40) cm long, 1-5 mm wide, flat, folded, or involute, erect and stiff or ascending and lax.

Panicles

10-30 cm long, (1)2-9 cm wide, open, nodding, green or tan, occasionally purple-tinged;

branches 2-12+ cm, most, except sometimes the uppermost, spikelet-bearing only towards the apices, with the basal (1/5)1/3-1/2 bare, filiform, flexuous, at least the lowest 1-3 whorls spreading or drooping.

(5)20-30(50) cm long, (0.5)1-2.5(5) cm wide, spikelike to open, often interrupted basally, green, purplish, or tawny, usually silvery-shiny;

branches with the spikelets evenly distributed.

Spikelets

6-12 mm, subsessile to pedicellate, pedicels to 2 cm, usually with 2-3 functional florets below 1-2 reduced florets;

rachilla internodes and hairs 1-2.5 mm;

disarticulation above the glumes, beneath the florets.

5-7.5 mm, sessile, subsessile, or on pedicels to 1.5(3.5) mm, with 2(3) florets;

rachilla internodes 0.5-1.5 mm;

rachilla hairs to 1 mm.

Glumes

unequal;

lower glumes 0.75-2(3) mm, subulate;

upper glumes 3.5-5 mm long, shorter than the lowest florets, 2-3 times as wide as the lower glumes, widest at or above the middle, ovate or obovate, rounded to the acuminate apices;

callus hairs to 1 mm;

lemmas 5-6 mm, broadly lanceolate, glabrous, bifid, teeth to 1.3 mm, awned, awns (7)9-14 mm, arising from above midlength to just below the teeth, exceeding the lemma apices, arcuate to flexuous;

paleas shorter than the lemmas;

anthers about 1 mm.

subequal to unequal, lanceolate, usually smooth, sometimes sparsely scabrous, sometimes pilose, with wide scarious margins, apices acute to acuminate, sometimes apiculate;

lower glumes 3-4(5.5) mm;

upper glumes 4-7 mm long, as long as or longer than the lowest florets, less than twice as wide as the lower glumes;

callus hairs to 1 mm;

lemmas 3-6(7) mm, narrowly to broadly lanceolate, glabrous or pilose, sometimes scabridulous, apices bifid, teeth usually shorter than 1 mm, awned, awns 3-8 mm, arising from the upper 1/3 of the lemmas and exceeding the apices, geniculate, twisted basally;

anthers 0.7-1.4 mm.

Caryopses

2.5-3.2 mm, densely to sparsely pubescent.

1.5-3(4) mm, glabrous.

2n

= 42.

= 14, 28, 42.

Trisetum cernuum

Trisetum spicatum

Distribution
from USDA
[WildflowerSearch map]
[BONAP county map]
from FNA
AK; AZ; CA; CO; CT; ID; MA; ME; MI; MN; MT; NC; NH; NM; NV; NY; OR; PA; RI; SD; TN; UT; VA; VT; WA; WI; WY; AB; BC; MB; NB; NL; NS; NT; NU; ON; QC; SK; YT; Greenland
[WildflowerSearch map]
[BONAP county map]
Discussion

Trisetum cernuum grows in moist woods, on stream banks, lake and pond shores, and floodplains of the western Flora region. The hairiness of the leaf sheaths varies, often within a plant.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Trisetum spicatum grows in moist meadows and forests, and on rock ledges, tundra slopes, and screes, at 0^1300 m. Its range includes both North and South America and Eurasia. Many infraspecific taxa have been based on the variation in vestiture and openness of the panicle, but none appears to be justified (see Finot et al. 2004 for a different opinion). Trisetum montanum Vasey appears to represent no more than an extreme phase. Trisetum spicatum differs from T. sibiricum in its pubescent sheaths and denser, usually narrower panicles.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 24, p. 748. FNA vol. 24, p. 748.
Parent taxa Poaceae > subfam. Pooideae > tribe Poeae > Trisetum Poaceae > subfam. Pooideae > tribe Poeae > Trisetum
Sibling taxa
T. aureum, T. canescens, T. flavescens, T. interruptum, T. melicoides, T. orthochaetum, T. sibiricum, T. spicatum, T. wolfii
T. aureum, T. canescens, T. cernuum, T. flavescens, T. interruptum, T. melicoides, T. orthochaetum, T. sibiricum, T. wolfii
Synonyms T. nutkanense T. triflorum subsp. molle, T. triflorum, T. subspicatum, T. spicatum var. pilosiglume, T. spicatum subsp. montanum, T. spicatum var. molle, T. spicatum subsp. molle, T. spicatum subsp. majus, T. spicatum var. maidenii, T. spicatum subsp. congdoni, T. montanum, T. molle
Name authority Trin. (L.) K. Richt.
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