In the genus Echinochloa, most of the important measurable characters overlap somewhat among species (Costea and Tardif 2002). Only the characters considered most useful are described below for separating dispersal units of some similar species from E. crus-galli.

Echinochloa colona (L.) Link

[Panicum colonum L. (USDA-ARS 2024); Echinochloa colonum (L.) Link (Boulos and el Hadidi 1984)]
Jungle rice (AOSA 2024; USDA-NRCS 2024)
Junglerice (DiTomaso and Healy 2007)
Jungle ricegrass (USDA-ARS 2024)
Awnless barnyard grass (Barkworth et al. 2003)

• The glumes and sterile floret lemma of E. colona are very thin and papery and lack the stiff, spike-like hairs found in E. crus-galli.
• The sterile floret lemma of E. colona is awnless.
• The caryopses of E. colona are generally smaller in size (1.2 – 1.6 mm long, 1.0 – 1.3 mm wide) compared to those of E. crus-galli (1.2 – 2.4 mm long, 1 – 1.8 mm wide (Barkworth et al. 2003).
• The caryopses of E. colona are yellowish or whitish coloured, whereas the caryopses of E. crus-galli are brownish-red or brownish-grey coloured (Costea and Tardif 2002; Barkworth et al. 2003).

Echinochloa esculenta (A. Braun) H. Schol

[Panicum esculentum A. Braun); E. crus-galli (L.) P. Beauv. subsp. utilis (Ohwi & Yabuno) T. Koyama; E. utilis Ohwi & Yabuno (Yabuno 1962; USDA-ARS 2024)]
Japanese barnyard grass (Scholz 1992)
Japanese millet (Wiersema and Léon 1999; Barkworth et al. 2003; USDA-ARS 2024)

• The spikelets of E. esculenta are broadly oval, egg-shaped or nearly round in outline and are generally wider (2 – 2.5 mm wide; Barkworth et al. 2003) than those of E. crus-galli (1.1 – 2.3 mm wide; Barkworth et al. 2003).
• The caryopses in E. esculenta are nearly round in outline, 1.2 – 2.3 mm long and wide, and the embryos are four-fifths to nearly the length of the caryopses, whereas the caryopses in E. crus-galli are usually narrower than they are long, and the embryos are three-fifths to seven-eights the length of the caryopses (Barkworth et al. 2003).
• E. esculenta is a cultivated species believed to have been originally derived from E. crus-galli about 4000 years ago in Japan (Yabuno 1962; deWet et al. 1983). It is used for cereal grain, fodder, and birdseed (deWet et al. 1983; Barkworth et al. 2003).

Echinochloa frumentacea Link

Siberian millet (Barkworth et al. 2003)
White panic (Barkworth et al. 2003)

• Mature spikelets of E. frumentacea are usually whitish or light yellow coloured, whereas those of E. crus-galli are pale green to light yellowish-brown coloured, sometimes purple tinged.
• The glumes and sterile floret lemma of E. frumentacea are very thin and papery and lack the stiff, spike-like hairs found in E. crus-galli.
• The sterile floret lemma of E. frumentacea is awnless.
• Although the caryopses of E. frumentacea are similar in size to E. crus-galli, they are yellowish or whitish coloured, whereas the caryopses of E. crus-galli are brownish-red or brownish-grey coloured (Costea and Tardif 2002; Barkworth et al. 2003).
• E. frumentacea is believed to have been originally derived from E. colona in India, and possibly Africa (Yabuno 1962; deWet et al. 1983; Barkworth et al. 2003). This cultivated species is grown for cereal grain, fodder, beer brewing, and for birdseed (Barkworth et al. 2003).

Echinochloa muricata (P. Beauv.) Fernald

American barnyard grass (Barkworth et al. 2003; USDA-ARS 2024)
Prickly barnyard grass (USDA-ARS 2024)
Rough barnyard grass (MWI 2024)

• The embryo of E. muricata is four-fifths to nine-tenths the length of the caryopsis, whereas the embryo of E. crus-galli is only three-fifths to seven-eights the length of the caryopsis (Gould et al. 1972).
• The body of the fertile lemma in E. muricata is hardened and gradually transitions into a firm, pointed, membranous tip, whereas in E. crus-galli the hardened portion of the fertile lemma is rounded at the apex, sharply differentiated from the thin, withering, membranous tip, and this transition point is delineated by a line of tiny hairs (Gould et al. 1972).
• The hardened fertile floret palea in E. muricata tapers to a firm point, while in E. crus-galli the hardened portion of the fertile floret palea has a rounded apex that transitions into a soft membranous tissue that usually folds over like a small flap (MWI 2024).

Echinochloa oryzicola (Vasinger) Vasinger

[Panicum oryzicola Vasinger; E. crus-galli (L.) P. Beauv. var. oryzicola (Vasinger) Ohwi; E. phyllopogon auct. pl. (USDA-ARS 2024)]
Late barnyard grass (Barkworth et al. 2003; USDA-ARS 2024)
Late watergrass (DiTomaso and Healy 2007)

• In E. oryzicola the lower(1st) glume is about one-half to three-fifths the length of the spikelet, whereas in E. crus-galli, the lower glume is usually not longer than one-half the length of the spikelet.
• The sterile floret lemma in E. oryzicola is often thickened and somewhat leathery (coriaceous), smooth, shiny, and with a few stiff hairs (rarely papery and with stiff hairs), while the sterile floret lemma of E. crus-galli is papery and has stiff, spine-like hairs along the nerves (Costea and Tardif 2002).
• The tip of the sterile floret lemma in E. oryzicola tapers to a sharp point, unawned or awn up to 1.5 mm (Barkworth et al. 2003), while in E. crus-galli the awn may be 0 – 50 mm in length.
• The embryo of E. oryicola can be up to nearly the length of the caryopsis, whereas the embryo in E. crus-galli is shorter (three-fifths to seven-eights the length of the caryopsis) (Barkworth et al. 2003).
• The stigmas are often persistent on the mature caryopsis of E. oryzicola (Costea and Tardif 2002).
• E. oryzicola is classified as a harmful organism by The Democratic People’s Republic of Korea and by The Republic of Korea (USDA-PCIT 2024).

Echinochloa oryzoides (Ard.) Fritsch

[Panicum oryzoides Ard.; E. crus-galli (L.) P. Beauv. var. oryzoides (Ard.) Lindm.; E. coarctata Kossenko; E. macrocarpa Vasinger; E. phllopogon (Stapf) Stapf ex Kossenko (USDA-ARS 2024)]
Early barnyard grass (Barkworth et al. 2003)
Early watergrass (DiTomaso and Healy 2007)
Hairy millet (USDA-ARS 2024)

• Nerves on the sterile floret lemma in E. oryzoides are usually visible the entire length of the lemma, while in E. crus-galli the nerves may only be visible towards the tip of the lemma or for the entire length of the lemma (Costea and Tardif 2002).
• In E. oryzoides the sterile floret lemma is almost always awned, the awns are 5 to 50 mm long, whereas in E. crus-galli the sterile lemma may be unawned or the awn may be up to 50 mm long (Barkworth et al. 2003; DiTomaso and Healy 2007).
• The caryopses of E. oryzoides are yellowish in colour, while in E. crus-galli the caryopses are brownish-red to brownish-grey in colour (Costea and Tardif 2002).
• E. oryzoides is classified as a harmful organism by The Democratic People’s Republic of Korea and by The Republic of Korea (USDA-PCIT 2024).