Plants annual. Culms 30-200 cm, spreading, decumbent
or stiffly erect; nodes usually glabrous or the lower nodes puberulent.
Sheaths glabrous; ligules absent, ligule region sometimes pubescent;
blades to 65 cm long, 5-30 mm wide, usually glabrous, occasionally sparsely
hirsute. Panicles 5-25 cm, with few-many papillose-based hairs at or
below the nodes of the primary axes, hairs sometimes longer than the spikelets;
primary branches 1.5-10 cm, erect to spreading, longer branches with
short, inconspicuous secondary branches, axes scabrous, sometimes also sparsely
hispid, hairs to 5 mm, papillose-based. Spikelets 2.5-4 mm long, 1.1-2.3
mm wide, disarticulating at maturity. Upper glumes about as long as the
spikelets; lower florets sterile; lower lemmas unawned to awned,
sometimes varying within a branch, awns to 50 mm; lower paleas subequal
to the lemmas; upper lemmas broadly ovate to elliptical, coriaceous portion
rounded distally, passing abruptly into an early-withering, acuminate, membranous
tip that is further demarcated from the coriaceous portion by a line of minute
hairs (use 25× magnification); anthers 0.5-1 mm. Caryopses
1.3-2.2 mm long, 1-1.8 mm wide, ovoid or oblong, brownish; embryos 59-86%
as long as the caryopses. 2n = 54.
Echinochloa crus-galli is a Eurasian species that is now widely established
in the Flora region, where it grows in moist, disturbed sites, including
rice fields. Some North American taxonomists have interpreted Echinochloa
crus-galli much more widely; others treat it as here, but recognize several
infraspecific taxa based on such characters as trichome length and abundance,
and awn length. There are several ecological and physiological ecotypes within
the species, but the correlation between most of these and the species morphological
variation has not been established, so no infraspecific taxa are recognized
here.