Bromus japonicus Thunb.

Family: Poaceae, Tribe: Bromeae

Pertinent Synonyms & Notes (particularly those used in California; go to GRIN for other synonyms)

Bromus abolini Drob., B. commutatus Schrad., B. unilateralis Schur.

Pertinent Common Names (particularly those used in California; go to GRIN for other common names)

Japanese brome

Primary Disseminule Type


Description (diagnostics are in brown)

Spikelets solitary, pedicelled, consisting of 7–15 fertile florets with similar-looking though diminished sterile florets at apex, ovate, slightly laterally compressed, 15–35(40) mm long, disarticulating below each fertile floret at maturity.

Glumes persistent, similar, shorter than spikelet, lanceolate, membranous, purplish, without keel, apices acute. Lower glume 4–7 mm long, 0.66 length of upper glume, 3–5-veined. Upper glume 5–8 mm long, 0.66–0.75 length of adjacent fertile lemma, 7-veined.

Fertile florets: rachilla persistent, callus short, blunt.

Lemma elliptic to obovate or obtrullate, 7–12 mm long x 1.2–2.2 mm wide, coriaceous, much thinner on margins (hyaline margins 0.3–0.9 mm wide), purplish, with rounded back (no keel), 7(9)-veined, midvein slightly ribbed, lateral veins obscure to somewhat ribbed, surface glabrous or pubescent, apex acute, entire or bifid, teeth <1 mm long, awn subapical, (5)8–13(16) mm long, slender, weak, curved outward or sometimes straight, somewhat twisted, flattened at the base, scabrous.

Palea 0.8 length of lemma, hyaline, keels ciliolate.

Caryopsis oblong, dorsiventrally compressed (flattened or with weakly inrolled edges), 6–7 mm long x ca. 1.7 mm wide, brown (sometimes purplish), apex fleshy and hairy, hilum linear, same length as caryopsis.

Similar Species

Similar Species Comparison Chart

Risk Assessment (codes in yellow or red indicate cause for concern; assessments are current as of mid-2011; click AUQP, NZBORIC, or NZBPI for access to the most recent versions of these databases and possible assessment changes)