Walla Walla County Extension

Weed of the Month

False Brome (Brachypodium sylvaticum)

False brome, also known as slender false brome, is an invasive bunch grass native to North Africa and Eurasia. The slender bunch grass grows 18 inches to two feet tall and tends to form large clumps.  It is a perennial that stays green longer into the summer than most brome grasses and may remain green throughout the winter when temperatures are mild.

False brome has flat, floppy leaves that are ¼ to ½ inches wide with hairs around the leaf margins as well as along the lower stems. The leaves are brighter green than most other bromes.   Between June and September, flower spikelets with straight awns, ½ to ¾ inches long, form on droopy stalks.  Seeds can be dispersed by wildlife or by humans on vehicles, boots, clothing, or equipment.

Unlike most grasses, false brome grows in shade as well as sun.  It grows well in moist or dry conditions and can be found from low elevations up to 3500 feet. 

False brome was first discovered in Oregon near Eugene in 1939 and has become is highly invasive in shaded woodlands, open prairies, and roadsides and can out-compete native forest understory and grassland vegetation.  As clumps spread and grow together, they form a solid mat that can overwhelm native vegetation.  Since it is unpalatable for grazing, it quickly reduces the productivity of rangeland and eliminates wildlife forage.  By out competing seedlings for moisture, it can threaten tree plantings as well.

Digging or pulling the plants can effectively control small, newly established populations of false brome but it can resprout from vegetative fragments.  For larger populations, repeated mowing may eliminate seed production.  Herbicide applications of glyphosate are most effective when used in the late spring or early summer when false brome is actively growing but has not yet set seed.  Follow up control measures before seed-set in early summer are needed for several following seasons to exhaust the seeds and small plants missed by initial control measures.

BE SURE TO FOLLOW ALL PESTICIDE LABEL INSTRUCTIONS AND PRECAUTIONS