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The City of Portland, Oregon

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Phone: 503-823-7740

Fax: 503-823-6995

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Alien Plant Invader: False Brome


false brome in forestThis month’s featured invasive plant might test your plant identification skills.  False brome (Brachypodium sylvaticum) is a bright green, fuzzy grass that is spreading across western Oregon and is up to no good.

While most grasses seem to avoid shady spots, false brome can thrive in many environments, including open and forested areas, roadsides, and stream banks. Once it makes itself at home, false brome can displace native understory plants and make it difficult for young trees to grow.  False brome may also increase fuel for wildfire and is not a good food source for native wildlife or livestock.

False brome made its debut in the U.S. near Eugene, Oregon in 1939, and has since spread across much of the Willamette Valley and SW Oregon. It is a required eradication species in Portland (see the Portland Plant List), a Class B noxious weed in Oregon, and a class A noxious weed in Washington.  While false brome is widespread in much of western Oregon, it is still relatively rare in Portland.  We need your help to keep it that way. 

How does false brome get around? The grass has abundant seeds that like to hitchhike on animal fur, hiker clothing and shoes, and vehicles. Seeds can also travel in waterways.  

     false brome flowers     false brome's fuzzy leaf

Grasses are tricky to identify, but false brome gives itself away with a few distinguishing characteristics.  False brome is a perennial bunchgrass that is capable of forming a solid carpet. It can reach up to 36 inches high, and it remains a distinct bright green color through much of the year. In June through September, the flower heads droop on the end of a wiry stem, and each flower in the flower head is attached to the stem with little to no stalk (see photo above left). 

False brome leaves are fuzzy, flat and wide, and when you hold them up to the light, you can see the hairs along the leaf edges. The lower stem is also fuzzy.

false brome plant

What can you do?  To remove false brome, dig up any small patches before they flower, but be sure to remove all the roots!  It’s also a good idea to cut off flower heads in June, to keep the seeds from spreading.  For larger patches, mid-summer to fall treatments with herbicides can be effective. For any treatment, follow up is highly recommended for several growing seasons. Before you take action, please contact Mitch Bixby at Environmental Services to discuss options and make sure the suspect is indeed false brome, and not a native grass. 


For more information, visit the City of Portland false brome website. King County, Washington also has more information and photographs.

Invasive species affect us all. They damage our forests, our streams and rivers, and our property.  Nationwide, damages associated with invasive species are estimated to be $120 billion each year.  In Oregon, the control of invasive weeds and the cost of the damages they create amounts to about $125 million each year.  We know that it costs a lot less to control new invasive plants before they become infestations, but we need everyone’s help.  Read more here about the problems caused by invasive species and why BES is particularly concerned about their impact on water quality.

Catch up on previous Alien Plant Invader posts:



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