Plants annual or perennial; with or without rhizomes. Culms 10-460 cm, prostrate, decumbent or erect, distal portions sometimes floating, sometimes rooting at the lower nodes; nodes usually glabrous; internodes hollow or solid. Sheaths open, compressed; auricles absent; ligules usually absent but, if present, of hairs; blades linear to linear-lanceolate, usually more than 10 times longer than wide, flat, with a prominent midrib. Inflorescences terminal, panicles of simple or compound spikelike branches attached to elongate rachises, axes not terminating in a bristle, spikelets subsessile, densely packed on the angular branches; disarticulation below the glumes (cultivated taxa not or tardily disarticulating). Spikelets plano-convex, with 2(3) florets; lower florets sterile or staminate; upper florets bisexual, dorsally compressed. Glumes membranous; lower glumes usually 1/4-2/5 as long as the spikelets (varying to more than 1/2 as long), unawned to minutely awn-tipped; upper glumes unawned or shortly awned; lower lemmas similar to the upper glumes in length and texture, unawned or awned, awns to 60 mm; lower paleas vestigial to well-developed; upper lemmas coriaceous, dorsally rounded, mostly smooth, apices short or elongate, firm or membranous, unawned; upper paleas free from the lemmas at the apices; lodicules absent or minute; anthers 3. Caryopses ellipsoid, broadly ovoid or spheroid; embryos usually 0.7-0.9 times as long as the caryopses. x = 9. Name from the Greek echinos, hedgehog, and chloa, grass, in reference to the bristly or often awned spikelets.

Echinochloa is a tropical to warm-temperate genus of 40-50 species that are usually associated with wet or damp places. Many of the species are difficult to distinguish because they tend to intergrade. Some of the characters traditionally used for distinguishing taxa, e.g., awn length, are affected by the amount of moisture available; others reflect selection by cultivation, e.g., non-disarticulation in grain taxa, mimicry of rice as weeds of rice fields. There are 13 species in the Flora region: five native and one possibly native, four established, two grown as commercial crops, and one in research.

In North America, the most abundant species appears to be the introduced, weedy Echinochloa crus-galli, which closely resembles the native E. muricata. The confusion between the two species has caused them to be treated as the same species. This confusion is likely reflected in the mapping of both Echinochloa crus-galli and E. muricata. Echinochloa frumentacea and E. esculenta are grown for grain in India and in China and Japan, respectively, but not in North America. Echinochloa oryzoides and E. oryzicola are weeds whose success and distribution reflects their adaptation to the periodic inundations of commercial rice fields.

Cytogenetic data suggest that E. frumentacea and E. esculenta are domesticated derivatives of E. colona and E. crus-galli, respectively (Yabuno 1962) and that E. oryzoides is very closely related to E. crus-galli (Yabuno 1984). Molecular work (Yamaguchi et al. (2005) are consisten with the cytogenetic daa with respect to the origin of the two domesticated taxa and places E. oryzoides in the unresolved clade that includes E. crus-galli and E. esculenta. Yabuno (1966) suggested that E. crus-galli is an allohexaploid produced by natural hybridization between the tetraploid E. oryzicola with a not-yet-discovered diploid species of Echinochloa and subsequent chromosome doubling. Studies using seed protein electrophoresis and isozyme analyses (Kim et al. 1989; González-Andrés et al. 1996; Asíns et al. 1999), and molecular studies involving RAPD markers and DNA sequences (Hilu 1994; Roy et al. 2000) or PCR-RFLP techniques (Yasuda et al. 2001), will help in clarifying the phylogenetic problems in Echinochloa, providing that proper attention is paid to the morphological characterization of the plant materials used and voucher specimens are made.

The map for Echinochloa polystachya has been amended (see comment), the correct varietal epithet for Echinochloa crus-pavonis should be var. macera [for additional comments on the correct varietal epithet, click here], and a reference supporting use of 'colona' for the epithet of E. colona added.

NOTE: In this treatment, measurements of the spikelets do not include the awns. The color of the caryopses is based on fully ripe caryopses. Chromosome numbers cited in this treatment are only those which are confidently believed to refer to the species described here.

1.   Echinochloa polystachya (Kunth) Hitchc.
Creeping River Grass

Plants perennial; not rhizomatous. Culms 1-2 m tall, to 1 cm thick, erect or decumbent and rooting at the lower nodes, upper portion sometimes floating distally; nodes glabrous or antrorsely villous. Sheaths mostly glabrous, minutely puberulent, or hispid, hairs papillose-based, throat hispid; ligules present on the lower leaves, 1-5 mm, of stiff hairs; blades 15-70 cm long, 5-13 mm wide, glabrous. Panicles 13-45 cm, erect, rachis nodes hispid, hairs 3-6.5 mm, papillose-based, internodes scabrous; primary branches 4-10 cm, subverticillate, ascending, nodes hispid, hairs 2.5-4 mm, papillose-based, internodes scabrous; secondary branches short, spikelets subsessile, in clusters. Spikelets 4-7 mm, hispid, hairs appressed, disarticulating at maturity. Lower glumes at least 1/2 as long as the spikelets; lower florets staminate; lower lemmas apiculate or awned, awns to 18 mm; lower paleas subequal to the lower lemmas, often purple; anthers of lower florets 1.5-3.6 mm, orange; upper lemmas 2.5-5 mm, elliptic or narrowly ovate, apices obtuse, with a membranous, soon-withering tip; anthers of upper florets shorter than those of the lower florets. Caryopses to 3 mm. 2n = 54.

Echinochloa polystachya grows in coastal marshes, often in standing water, from Texas to Louisiana, and south through Mexico and the Caribbean islands to Argentina. Echinochloa polystachya var. polystachya has glabrous culms and leaf sheaths; Echinochloa polystachya var. spectabilis (Nees ex Trin.) Mart. Crov. has swollen, pubescent cauline nodes and pubescent leaf sheaths.

December 2003: Prof. Daniel B. Ward wrote to Barkworth stating that the record of Echinochloa polystachya from Florida is based on a cultivated specimen. The map on the Web site and the above comment have been amended to reflect his correction.

2.   Echinochloa pyramidalis (Lam.) Hitchc. & Chase
Antelope Grass

Plants perennial; with short, scaly rhizomes. Culms 1-4.6 m tall, to 2 cm thick, geniculate or long-prostrate and rooting at the lower nodes, often floating distally; lower and upper nodes glabrous. Sheaths mostly glabrous, but usually ciliate at the throat; ligules present on the lower leaves, 1-5 mm, of stiff hairs, reduced or absent on the upper leaves; blades 8-75 cm long, 5-30 mm wide. Panicles 15-40 cm, nodes and internodes scabrous; primary branches 2-7.5 cm, solitary to fascicled, erect or ascending, simple or compound, nodes and internodes glabrous or hispid, hairs to 4 mm, papillose-based. Spikelets 2.5-4 mm long, 1-1.8 mm wide, disarticulating at maturity, finely pubescent or glabrous, greenish to purple at maturity. Lower florets staminate; lower lemmas unawned, acute to acuminate or long cuspidate; anthers of lower florets 1-1.5 mm; upper lemmas apiculate to long cuspidate. Caryopses about 2 mm. 2n = 54, 72.

Echinochloa pyramidalis is native to Africa, where it is used both as a cereal and a pasture grass. It has been grown experimentally in Gainesville, Florida, but it is not established in North America.

3.   Echinochloa paludigena Wiegand
Florida Barnyard Grass

Plants annual. Culms to 150 cm, erect. Sheaths glabrous; ligules absent; blades 15-60 cm long, 8-20 mm wide, scabrous adaxially. Panicles 8-40 cm, erect to slightly drooping, rachis nodes hispid, hairs papillose-based; primary branches 2-19 cm, erect to spreading, often widely spaced, longer branches with secondary branching. Spikelets 3.3-4.5 mm long, 2.4-2.6 mm wide, disarticulating at maturity, greenish or purplish, scabrous and hispid, hairs to 1 mm, often papillose-based. Upper glumes about as long as the spikelets; lower florets staminate; lower lemmas usually awned, awns 1-15 mm, purplish; lower paleas well-developed; upper lemmas broadly ovate, narrowing abruptly to the acute or acuminate apices; anthers of upper florets 1.2-1.7 mm. Caryopses 1.5-1.8 mm. 2n = unknown.

Echinochloa paludigena is native to swamps, riverbanks, and other wet habitats. Reports from Texas and Louisiana appear to be based on misidentifications; Wunderlin (1988) considers E. paludigena as a Florida endemic.

4.   Echinochloa muricata (P. Beauv.) Fernald
American Barnyard Grass

Plants annual. Culms 80-160 cm, erect or spreading, sometimes rooting at the lowest nodes, often developing short axillary flowering shoots at most upper nodes when mature; lower nodes glabrous or puberulent; upper nodes glabrous. Sheaths glabrous; ligules absent; blades 1-27 cm long, 0.8-30 mm wide. Panicles of primary culms 7-35 cm, rachises and branches glabrous or hispid, hairs to 3 mm, papillose-based; primary branches 2-8 cm, usually spreading and rather distant, often with secondary branches. Spikelets 2.5-5 mm, disarticulating at maturity, usually purple or streaked with purple, usually hispid, hairs papillose-based. Upper glumes about as long as the spikelets; lower florets sterile; lower lemmas unawned or awned, awns to 16 mm; lower paleas well-developed; upper lemmas broadly obovoid or orbicular, narrowing to an acute or acuminate coriaceous portion that extends into the membranous tip, boundary between the coriaceous and membranous portions not marked by minute hairs; anthers 0.4-1.1 mm. Caryopses 1.2-2.5 mm, broadly obovoid or spheroid, yellowish; embryos 1.4-2 mm, 80-91% as long as the caryopses. 2n = 36.

Echinochloa muricata is native to North America, growing from southern Canada to northern Mexico in moist, often disturbed sites (but not rice fields). It resembles E. crus-galli in gross morphology and ecology, but differs consistently by the characters used in the key. The two varieties tend to be distinct, but there is some overlap in both morphology and geography.

Echinochloa muricata var. microstachya Wiegand
Échinochloa de l'Ouest

Spikelets 2.5-3.8 mm. Lower glumes 0.9-1.6 mm; upper glumes 2.8-3.8 mm; lower lemmas unawned or awned, awns to 10 mm; anthers 0.4-0.7 mm.

Echinochloa muricata var. microstachya is the common variety in the western part of North America, extending east to the Missouri River and the Texas panhandle.

Echinochloa muricata (P. Beauv.) Fernald var. muricata
Échinochloa Piquant

Spikelets 3.5-5 mm. Lower glumes 1-2.6 mm; upper glumes3-5 mm; lower lemmas usually awned, awns 6-16 mm, occasionally unawned; anthers 0.5-1.1 mm.

Echinochloa muricata var. muricata is the common variety in eastern North America.

5.   Echinochloa walteri (Pursh) A. Heller
Coast Barnyard Grass

Plants annual. Culms (30)50-200+ cm tall, to 2.5 cm thick; nodes pilose or villous, upper nodes usually with sparser and shorter pubescence, occasionally glabrous. Lower sheaths usually hispid, hairs papillose-based, sometimes just papillose; upper sheaths hispid or glabrous; ligules absent; blades to 55 cm long, 10-35(60) mm wide, scabrous. Panicles 8.5-35 cm, erect to slightly drooping, nodes hispid, hairs 3.5-5 mm, papillose-based, sometimes sparsely so, internodes usually glabrous, sometimes hispid, hairs papillose-based; primary branches 1-10 cm, loosely erect, not concealed by the spikelets, nodes usually hispid, hairs papillose-based, sometimes glabrous, internodes scabrous, sometimes also sparsely hispid, hairs papillose-based; secondary branches present on the longer primary branches. Spikelets 3-5 mm, disarticulating at maturity, scabrous to variously muricate and hairy, hairs usually not papillose-based, margins sometimes with a few papillose-based hairs. Lower glumes usually more than 1/2 as long as the spikelets, abruptly narrowing to a fine, 0.5 mm point; lower florets sterile; lower lemmas usually awned, awns 8-25(60) mm; lower paleas subequal to the lower lemmas; upper lemmas 3-5 mm long, about 1.5 mm wide, not or scarcely exceeding the upper glumes, narrowly ovate to elliptical, coriaceous portion subacute, tips acuminate, membranous, without a line of hairs at the base of the tip; anthers 0.6-1(1.2) mm. Caryopses 1.2-1.8 mm, brownish; embryos 52-77% as long as the caryopses. 2n = 36.

Echinochloa walteri grows in wet places, often in shallow water and brackish marshes. It is a native species, found in both disturbed and undisturbed sites although not in rice fields. Occasional specimens of E. walteri with glabrous lower sheaths and short awns can be distinguished from E. crus-pavonis by their less dense panicles.

6.   Echinochloa crus-pavonis (Kunth) Schult.
Gulf Barnyard Grass

Plants annual or short-lived perennials. Culms 30-150 cm; nodes glabrous. Sheaths glabrous, often purplish; ligules absent; blades 12-60 cm long, 10-25 mm wide, glabrous. Panicles 10-30 cm, erect or drooping, nodes sparsely hispid, hairs papillose-based, internodes glabrous; primary branches to 14 cm, nodes sometimes sparsely hispid, hairs papillose-based, internodes usually glabrous; secondary branches to 3 cm. Spikelets 2.5-3.4 mm long, 1.2-1.4 mm wide, disarticulating at maturity. Upper glumes subequal to the spikelets; lower florets sterile; lower lemmas unawned or awned, awns 3-10(15) mm, curved; lower paleas absent, vestigial, or well-developed; upper lemmas narrowly elliptic, not or scarcely exceeding the upper glumes, acute or obtuse, with a well-differentiated, early-withering tip, glabrous or pubescent at the base of the tip, hairs not forming a line across the base; anthers 0.5-0.7 mm. Caryopses 1.2-1.5 mm long, 1-1.3 mm wide; embryos 50-70% as long as the caryopses. 2n = 36.

Echinochloa crus-pavonis is a native species found in scattered locations from British Columbia to Arizona, east to Florida, and south into South America. It favors marshes and wet places at lower elevations, often being found in the water.

Echinochloa crus-pavonis (Kunth) Schult. var. crus-pavonis

Panicles usually drooping. Lower paleas 1/2 or more as long as the lower lemmas.

Echinochloa crus-pavonis var. crus-pavonis is generally the more southern of the two varieties, extending through Mexico and the Caribbean to Bolivia and Argentina. It appears, presumably as an adventive species, as far north as Humboldt County, California.

Echinochloa crus-pavonis var. macera (Wiegand) Gould

Panicles usually erect, stiff. Lower paleas absent or much less than 1/2 as long as the lower lemmas.

Echinochloa crus-pavonis var. macera extends south only as far as northern Mexico.

7.   Echinochloa oplismenoides (E. Fourn.) Hitchc.
Chihuahuan Barnyard Grass

Plants annual. Culms to 100 cm, erect, succulent, glabrous, branching from the lower nodes. Sheaths glabrous or hispid with papillose-based hairs; ligules absent or the ligule region pubescent; blades 10-35 cm long, 5-10 mm wide. Panicles 15-30 cm, narrow; primary branches appressed to ascending, with papillose-based hairs at the base of the spikelets. Spikelets 4-5 mm, disarticulating at maturity. Glumes with hairs over the veins, glabrous, scabrous, or hispid between the veins; upper glumes about equal to the spikelets, muticous or awned, awns to 1 mm; lower florets sterile; lower lemmas unawned or awned, awns 8-16(50) mm; lower paleas absent or hyaline and subequal to the lemmas; upper lemmas 4-4.5 mm long, 1.7-1.9 mm wide, elliptic; anthers 0.5-0.7 mm, purple. Caryopses2.7-2.9 mm long, 1.7-1.8 mm wide, elliptic in outline, mucronate; embryos about 75% as long as the caryopses; hila obovate. 2n = unknown.

Echinochloa oplismenoides was first found in the United States, in southern Arizona, in 1993 (Fishbein 1995). It was previously known only from Mexico, with a range that extends from northwestern Mexico to Guatemala. The southern Arizonan plants were found near a cattle tank in wet grasslands. Fishbein stated that it was impossible to tell whether they represented a previously overlooked native species or an introduction.

8.   Echinochloa colona (L.) Link
Awnless Barnyard Grass

Plants annual; erect or decumbent, cespitose or spreading, rooting from the lower cauline nodes. Culms 10-70 cm; lower nodes glabrous or hispid, hairs appressed; upper nodes glabrous. Sheaths glabrous; ligules absent, ligule region frequently brown-purple; blades 8-22 cm long, 3-6(10) mm wide, mostly glabrous, sometimes hispid, hairs papillose-based on or near the margins. Panicles 2-12 cm, erect, rachises glabrous or sparsely hispid; primary branches 5-10, 0.7-2(4) cm, erect to ascending, spikelike, somewhat distant, without secondary branches, axes glabrous or sparsely hispid, hairs 1.5-2.5 mm, papillose-based. Spikelets 2-3 mm, disarticulating at maturity, pubescent to hispid, hairs usually not papillose-based, tips acute to cuspidate. Lower glumes about 1/2 as long as the spikelets; upper glumes about as long as the spikelets; lower florets usually sterile, occasionally staminate; lower lemmas unawned, similar to the upper glumes; lower paleas subequal to the lemmas; upper lemmas 2.6-2.9 mm, not or scarcely exceeding the upper glumes, elliptic, coriaceous portion rounded distally, passing abruptly into a sharply differentiated, membranous, soon-withering tip; anthers 0.7-0.8 mm. Caryopses 1.2-1.6 mm, whitish; embryos 63-83% as long as the caryopses. 2n = 54.

Echinochloa colona is widespread in tropical and subtropical regions. It is adventive and weedy in North America, growing in low-lying, damp to wet, disturbed areas, including rice fields. The unbranched, rather widely-spaced panicle branches make this one of the easier species of Echinochloa to recognize.

Hitchcock (1913) considered that colonum was a non-declining contraction, but dictionaries of Linnaeus' time treated it as a declining adjective. Because Linnaeus was the first to name the species (as Panicum colonum), it seems best to follow the practice considered correct in his day; hence E. colona. (See also Nicolson 1986.)

9.   Echinochloa frumentacea Link
Siberian Millet, White Panic

Plants annual. Culms 70-150 cm, erect, glabrous. Sheaths glabrous; ligules absent; blades 8-35 cm long, 3-20(30) mm wide, glabrous. Panicles 7-18 cm, erect to slightly drooping at maturity, rachises not or only sparsely hispid, nodes with papillose-based hairs; branches numerous, appressed or ascending, spikelike, not or only sparsely hispid, hairs papillose-based; primary branches 1.5-4 cm, glabrous or sparsely hispid, hairs to 3 mm, papillose-based; secondary branches, if present, usually concealed by the densely packed spikelets; longer pedicels 0.2-0.5 mm. Spikelets 3-3.5 mm, often with 1 sterile and 2 bisexual florets, not disarticulating at maturity (particularly those near the bases of the panicles), scabrous or short-hispid but without papillose-based hairs, green and pale at maturity, apices usually obtuse, varying to acute. Upper glumes narrower and shorter than the upper lemmas; lower florets sterile; lower lemmas unawned; lower paleas subequal to the lower lemmas; upper lemmas 2.5-3 mm, ovate to elliptic, coriaceous portion terminating abruptly at the base of the membranous tip; anthers 0.8-1 mm. Caryopses 1.7-2.2 mm long, 1.6-1.8 mm wide, whitish; embryos 66-86% as long as the caryopses. 2n = 36 [J.D. Munshi, J.K. Pal, V. Bansikar, and N. Pandit. 1994. Eco-cytological studies of Echinochloa frumentacea (Roxb.) Link of Diara Lands of Bhagalpur, Bihar. Proc. Indian Sci, Congr. 81:112], 54.

Echinochloa frumentacea originated in India, and possibly also in Africa. It is grown for grain, fodder, and beer, although not as extensively as in the past. It is found occasionally in the contiguous United States and southern Canada, the primary source being birdseed mixes. It used to be confused with E. esculenta, from which it differs in its whitish caryopses and proportionately smaller embryos. Hybrids between E. frumentacea and E. colona are partially fertile; those with E. esculenta are sterile.

10.   Echinochloa crus-galli (L.) P. Beauv.
Barnyard Grass, Échinochloa Pied-de-Coq

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.

11.   Echinochloa esculenta (A. Braun) H. Scholtz
Japanese Millet

Plants annual. Culms 80-150 cm tall, 4-10 mm thick, glabrous. Sheaths glabrous; ligules absent, ligule region sometimes pubescent; blades 10-50 cm long, 5-25 mm wide. Panicles 7-30 cm, dense, rachis nodes densely hispid, hairs papillose-based, internodes scabrous; primary branches 2-5 cm, erect or spreading, simple or branched, often incurved at maturity, nodes hispid, hairs papillose-based, internodes usually scabrous; longer pedicels 0.5-1 mm. Spikelets 3-4 mm long, 2-2.5 mm wide, not or only tardily disarticulating at maturity, obtuse to shortly acute, purplish to blackish-brown at maturity. Upper glumes narrower and shorter than the upper lemmas; lower florets sterile; lower lemmas usually unawned; lower paleas shorter and narrower than the lemmas; upper lemmas longer and wider than the upper glumes, broadly ovate to ovate-orbicular, shortly apiculate, exposed distally at maturity; anthers 1-1.2 mm. Caryopses 1.2-2.3 mm, brownish; embryos 84-96% as long as the caryopses. 2n = 54.

Echinochloa esculenta was derived from E. crus-galli in Japan, Korea, and China. It is cultivated for fodder, grain, or birdseed. It has sometimes been included in Echinochloa frumentacea, from which it differs in its brownish caryopses and longer pedicels. Hybrids between E. crus-galli and E. esculenta are fully fertile, but those with E. frumentacea are sterile.

12.   Echinochloa oryzoides (Ard.) Fritsch
Early Barnyard Grass

Plants annual. Culms 40-120 cm, erect, densely tufted; nodes glabrous. Sheaths glabrous; ligules absent; blades lax or drooping, 7-20 cm long, 4-12 mm wide, mostly glabrous. Panicles 8-17(25) cm, lax, horizontal to strongly drooping, rachis nodes hispid, hairs to 4 mm, papillose-based, internodes glabrous; primary branches to 5 cm, appressed to the rachises, mostly simple, glabrous or sparsely hispid, hairs to 3.5 mm, papillose-based, particularly at the nodes. Spikelets 3.7-7 mm long, 1.9-2.4 mm wide, disarticulating at maturity, broadly ovate to ovate. Lower glumes usually 1/4-2/5 as long as the spikelets, occasionally 1/2 as long or longer; upper glumes subequal to the spikelets; lower florets sterile; lower lemmas similar in size to the spikelet, usually awned, awns to 5 cm; lower paleas well-developed; upper lemmas 3.5-4.5 mm, similar in length and width to the upper glumes, broadly elliptic to ovate, with an acute, greenish tip; anthers to 0.8 mm. Caryopses 1.9-3 mm, light brown or tan; embryos 70-85% as long as the caryopses. 2n = 54.

Echinochloa oryzoides is a common weed of rice fields throughout the world, growing in the flooded portions of the fields. It was included in Echinochloa oryzicola by Gould et al. (1972), but it differs in its shorter embryo, lax, strongly drooping panicle, and earlier (June-July) flowering period. This flowering period is also earlier than that of Oryza. In addition, E. oryzoides is usually conspicuously awned, having longer awns than even the awned variants of E. oryzicola, and it is rarely obviously pubescent on the cauline nodes, leaf sheaths, and collars. The earliest known collection of Echinochloa oryzoides in the United States was made in 1925 (Barrett and Seaman 1980).

13.   Echinochloa oryzicola (Vasinger) Vasinger
Late Barnyard Grass

Plants annual. Culms 40-150 cm, erect or nearly so, densely tufted; lower nodes usually antrorsely scabrous or villous; upper nodes glabrous. Lower sheaths densely pubescent; upper sheaths glabrous or pubescent at the throat, and sometimes on the collar; ligules absent; blades stiff, ascending, lower blades pubescent, upper blades usually glabrous. Panicles 8-20 cm, erect to slightly drooping, rachis nodes hispid, with papillose-based hairs to 5.6 mm, internodes usually scabrous, sometimes also with a few papillose-based hairs; primary branches to 4 cm. Spikelets 4-6 mm, ovoid to ellipsoid, disarticulating at maturity. Lower glumes usually at least 1/2 as long as the spikelets; upper glumes equaling or exceeding the upper florets; lower florets sterile; lower lemmas often thickened and somewhat coriaceous, unawned or awned, awns to 1.5 mm; lower paleas well-developed; 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 minute hairs (use 25× magnification); anthers 0.9-1.2 mm. Caryopses 1.7-2.6 mm, brownish; embryos 89-98% as long as the caryopses. 2n = 36.

Like Echinochloa oryzoides, Echinochloa oryzicola is an introduced weed of rice fields, where it grows in the flooded portion, with the rice. The two are quite distinct, with E. oryzicola flowering after Oryza and having a longer embryo and an erect panicle. It is also more likely to have evidently pubescent cauline nodes, leaf sheaths, and collars than E. oryzoides and is never conspicuously awned.