Nassella trichotoma
Nassella viridula
serrated tussock, serrated tussockgrass, yass tussockgrass
green nassella, green needlegrass
20-60 cm tall, about 1 mm thick, erect, internodes glabrous;
nodes 2-4, pubescent.
35-120 cm, erect or geniculate basally, internodes mostly glabrous, pubescent below the lower nodes;
nodes 2-3, glabrous.
glabrous, smooth;
collars glabrous, without tufts of hair at the sides;
ligules 0.5-2.5 mm, glabrous, obtuse;
blades 15-45 cm long, 0.2-0.6 mm wide, convolute, stiff, scabridulous.
mostly glabrous, margins usually ciliate;
collars of basal leaves hispidulous, with tufts of hair at the sides, hairs 0.5-1.8 mm, collars of flag leaves glabrous or sparsely pubescent;
ligules 0.2-1.2 mm, glabrous, truncate to rounded;
blades 10-30 cm long; 1.5-3 mm wide, flat to convolute, abaxial surfaces scabridulous, glabrous, adaxial surfaces glabrous.
8-25 cm, open, lax, sparse;
branches 2-6 cm, with 1-8 spikelets;
pedicels 3-12 mm.
2.9-7.2 cm, loosely contracted;
branches 1-4 cm, appressed or ascending, with 3-7 spikelets;
pedicels 1-9 mm.
subequal, 4-10 mm long, 0.9-1.2 mm wide, narrowly lanceolate, scabridulous, apices aristate;
florets 1.5-2.5 mm long, 0.7-0.9 mm wide, terete, widest near the top;
calluses 0.1-0.3 mm, acute, strigose, hairs reaching to midlength on the lemmas;
lemmas strongly tuberculate, particularly distally, mostly glabrous, narrowing abruptly to the crown, midveins pubescent proximally;
crowns about 0.5 mm long, about 0.2 mm wide, straight-sided, rims entire or irregularly lacerate, glabrous;
awns 15-35 mm, eccentric, straight to twice-geniculate;
anthers 3, 1-1.5 mm.
subequal, 6.8-13 mm long, 1-2.1 mm wide, narrowly lanceolate, glabrous, apiculate;
florets 3.4-5.5 mm long, 1-1.2 mm wide, terete;
calluses 0.7-1.4 mm, moderately sharp, strigose;
lemmas papillose, evenly pubescent, not constricted below the crown;
crowns 0.4-0.5 mm long, 0.3-0.5 mm wide, not conspicuous, straight-sided, rims with 0.5-0.75 mm hairs;
awns 19-32 mm, evidently twice-geniculate, terminal segment straight;
anthers (0.8)2-3 mm, sometimes penicillate.
about 1.2 mm, oblong, dark brown.
about 3.5 mm.
= 36.
= 82, 88.
Nassella trichotoma
Nassella viridula
Nassella trichotoma is a native of South America, and has been accidentally introduced into the United States. Because it is on the U.S. Department of Agriculture's noxious weed list, all known populations have been eliminated. New populations should be reported to the Department.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Nassella viridula grows in grasslands and open woods, frequently on sandy soils. It is the most widespread species of Nassella in North America. Its morphology, distribution, and high chromosome number suggest that it may be an alloploid between Nassella and Achnatherum. It is included in Nassella because it resembles Nassella more than Achnatherum in the characters distinguishing the two genera. It differs from Achnatherum robustum in its tightly convolute lemmas and in having glabrous to sparsely pubescent collars on its flag leaves. It differs from the hybrid with Achnatherum hymenoides, ×Achnella caduca, in its less saccate glumes, shorter lemmas hairs, and shorter paleas.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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