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nodding false oat, nodding oatgrass, nodding trisetum

Siberian oatgrass, Siberian trisetum

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

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

15-40(65) cm, solitary, decumbent;

nodes glabrous.

Sheaths

smooth;

ligules 1-3.5 mm, truncate or slightly higher in the center, often lacerate;

blades 8-15(24) cm long, 2.5-7 mm wide, flat, erect or ascending, stiff or lax, smooth.

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.

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.

2-12(16) cm long, (1)2-3(6) cm wide, ovate-spicate, sometimes basally interrupted, yellowish brown, often mottled, shiny;

branches usually 0.1-2(4) cm, appressed-ascending, the spikelets distal;

disarticulation above the glumes, beneath the florets.

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.

5-8 mm, subsessile or pedicellate, pedicels to 4 mm, with 2(3) florets;

rachilla internodes usually 1-2 mm;

rachilla hairs 0.5-1 mm, often curly and tangled.

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.

lanceolate, glabrous;

lower glumes 3-4.5 mm;

upper glumes 5-8 mm;

callus hairs about 0.5 mm;

lemmas 4.5-7 mm, glabrous, apices minutely bifid, teeth shorter than 1 mm, awned, awns 4-10+ mm, arising from the upper 1/3, exceeding the lemma apices, flexuous, curved, or bent and twisted basally;

paleas subequal to or as long as the lemmas;

anthers 2-3.5 mm.

Caryopses

2.5-3.2 mm, densely to sparsely pubescent.

1-2 mm, ovate, smooth, brown.

2n

= 42.

= 14, 28.

Trisetum cernuum

Trisetum sibiricum

Distribution
from USDA
[WildflowerSearch map]
[BONAP county map]
from FNA
AK; YT
[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 sibiricum grows on coastal beaches and creek banks, and in moist meadows and open forests, from sea level to 300+ m. It is often abundant and has significant value as a pasture plant. Circumpolar in distribution, in the Flora region it grows in Alaska and the Yukon Territory. Most North American plants belong to Trisetum sibiricum subsp. litorale Rupr. ex Roshev., having culms 15-30 cm tall, leaf blades 2.5-4 mm wide, panicles 3-5 cm long and 2-3 cm wide, branches to 2 cm long, and lemma awns 5-8 mm long. Trisetum sibiricum Rupr. subsp. sibiricum occurs in the Yukon Territory and Eurasia. It differs from T. spicatum in its smooth culms and leaves, and its broad, less dense panicles.

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

Source FNA vol. 24, p. 748. FNA vol. 24, p. 750.
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. spicatum, T. wolfii
Synonyms T. nutkanense
Name authority Trin. Rupr.
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