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Picture of growth habit.

Scientific Name

Bromus japonicus Thunb.

Common Name(s)

Japanese brome

Tribe / Family Name

Bromeae

Flowering Period

May to July

Symbol

BRAR5

Description

Japanese brome is an introduced cool-season winter annual bunchgrass that spreads by seed and tillers. Culms usually range from 30–70 cm in height. Its inflorescence is an open, nodding to drooping panicle 10–22 cm long with pedicels usually longer than the spikelets. Spikelets are 20–40 mm long, lanceolate, round to moderately literately compressed, 6- to 12-flowered, and awned (awns 6–11 mm long, twisted and geniculate at maturity, and arising below the lemma tips). Ligules are up to 2.2 mm long, membranous, obtuse, lacerate, and pilose.

General Info

Japanese brome can be found in disturbed areas such as roadsides, fields, waste places, overgrazed rangelands, as well as valleys and foothills, plains, and montane sites.

Similar Species

Japanese brome may look similar to soft brome (Bromus hordeaceus). However, the inflorescence of Japanese brome is usually nodding to drooping over and does not appear to be erect like soft brome. Also, Japanese brome has large, smooth or scabrous spikelets with awns that become twisted and geniculate at maturity, and soft brome has small, hairy spikelets with straight awns, but become recurved at maturity. Other similar species include cheatgrass (Bromus tectorum) and rattlesnake brome (Bromus briziformis), which also have inflorescences that appear to be nodding to drooping over. However, cheatgrass has long, straight awns, and rattlesnake brome is awnless or short awned.

Picture of growth habit.

Picture of growth habit.

Close-up picture of an open, nodding to drooping panicle inflorescence.

Close-up picture of an open, nodding to drooping panicle inflorescence.

Close-up picture of spikelet.

Close-up picture of spikelet.

Close-up picture of membranous ligule.

Close-up picture of membranous ligule.

Illustration for field brome. USDA-NRCS PLANTS Database / Britton, N.L., and A. Brown. 1913. <i>An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols</i>. Charles Scribner's Sons, New York. Vol. 1: 279.

Illustration for field brome. USDA-NRCS PLANTS Database / Britton, N.L., and A. Brown. 1913. <i>An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols</i>. Charles Scribner's Sons, New York. Vol. 1: 279.

Distribution map of Japanese brome. USDA PLANTS Database, 2022.

Distribution map of Japanese brome. USDA PLANTS Database, 2022.