Plants annual. Culms 10-45 cm, compressed. Blades 6-25 cm
long. Panicles digitate, with (1)2-3 branches; branches 1-6(8) cm
long, 5-14 mm wide, oblong. Spikelets 8-10 mm, with 5-9(11) florets. Glumes
unequal; lower glumes 2-3 mm; upper glumes 3-4 mm; lemmas
4-5 mm. 2n = 18.
Eleusine tristachya was originally thought to be native to tropical Africa
and introduced into tropical America, but it occurs in Africa only as a rare adventive.
It is now considered to be native to tropical America. In the 1800s and early
1900s, it was found on ballast dumps at various ports and transportation centers
in the United States. More recently, it has been found as a weed in the Imperial
Valley of California (Hilu 1980). All records of collections outside of California
appear to be historical, with no populations persisting. That from Texas, for
instance, was made from a plant growing in a range management area associated
with one of the Texas A&M University farms. Although not deliberately cultivated,
it probably was an escape. The species has not been collected since in Texas.