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Invasive Plant: False Brome

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Photo shows grass plant covering the ground of a forested area.
In the Portland area, false brome is mostly found in the Clackamas River basin, but patches have been treated in the Gorge, Forest Park, Mt. Tabor, and Powell Butte. These locations show how this plant can be carried along hiking trails or in flowing water.
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At a Glance

  • Scientific name: Brachypodium sylvaticum
  • Annual, perennial, or biennial? Perennial
  • Conditions it likes best: Grows well in bright, open spaces like meadows or oak savannahs, but in the Portland area, it is commonly found in shaded forests.
  • How it spreads: False brome is spread by people and large wildlife such as deer. Cleaning your boots after hiking, checking your dog’s fur, and scrubbing down your tires after driving in forests are all excellent ways to keep from spreading false brome (and other weeds).
  • How it causes damage: Dominates an area by keeping other plants from getting light and nutrients. Fewer animals live there because the plants they depend on don’t survive. In forests, false brome keeps tree seedlings from growing into adult trees.
  • Best time and way to manage: Digging small numbers of plants in June works well. Larger numbers of plants should have flowerheads cut in June and herbicide treatment in the fall.
  • Oregon Department of Agriculture noxious weed rank: B
  • Report patches of this plant? Yes. City code lists this as a Required Eradication species. Report all sightings to Portland’s Environmental Services. Contact information is on this page. Management of this species is required, but free help is available.

How to Identify False Brome

Photo shows long, green, grass-like leaves that have a fuzzy texture.
False brome has fuzzy hairs along the edges of its leaves.

Falsebrome is a bunch grass, brought to Oregon as an experimental grazing plant in the late 1930s. Since then, it has spread throughout northwestern Oregon and is an important nuisance in the Willamette Valley.

Spring. Seedlings emerge April through May. Single false brome plants stay in compact bunches that grow up to 3 feet tall. Leaves are unusually bright green and stay green into November. The leaves are also known for their softness and fuzziness. 

Summer–Fall. False brome doesn’t spread along the ground like many weedy grasses. Instead, it creates large numbers of seeds, which then get caught in fur or socks, or tracked out by mud in shoes or tires. False brome flowers in June and July, with very droopy flower clusters growing off the main stem. Seeds are ripe by August.

Winter. It is very hard to identify false brome in the winter, unless you are familiar with the leaves. Green grasses in the winter may be false brome or maybe not.  

How and When to Remove False Brome

  • Manual. Dig up false brome, being careful to remove all roots. Cut seedheads in June to reduce the chance of plants making seed.
  • Herbicide. Low rates of certain herbicides applied in the fall will kill adult plants. Herbicide after a June flower cutting might work, but it might hurt other plants, too.
  • Check: Check the site for new plants at least once a year and especially for the first 2-3 years after removal.
  • Replant. After a year or two of managing this plant, consider planting native or less aggressive non-native plants.

Prevention is Best Practice

Clean your boots, pets, and maybe even your tires when you finish a hike or trail ride in Pacific Northwest natural areas, or if you have invasive plants on your own property. Cleaning boots and pets keeps invasive plants from spreading to new places. Be careful when trading plants with neighbors and fellow gardeners to make sure you’re not trading this or any other plant of concern.

Be Aware of Look-alikes

Photo shows small seed pods along the tip of a stem against a white background.
False brome seedheads attach directly to the main stem. Single seedheads alternate along the stem, causing a distinctive droop.

Grasses are difficult plants to identify, and even professionals get it wrong. Look for fuzzy leaves, seeds directly attached to the main stem, and bright green bunches of leaves. True bromes have flower/seed clusters attached to a short stem that attaches to the main stem. If you think you might have found false brome, contact  Environmental Services (contact information on this page) or your county’s noxious weed program.

Properly Dispose of Invasive Plants

To prevent spreading invasive plants:

  • Never place plants or seeds in your compost or yard debris.
  • Never throw pulled plants on the ground or into the street or sidewalk.
  • Put all pulled plants, bulbs, or seeds into a plastic bag and put the bag in the trash.
  • Wash all garden tools and gloves.

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