What is the species?
- Brachypodium sylvaticum (false-brome)
- ODA “B” rank
False-brome is a perennial bunch grass introduced as an experimnetal forage plant in 1939. Since then, it has expanded through much of the mid and lower Willamette Valley and is moving down several Portland rivers (Willamette, Clackamas, Tanner Creek and others in the Gorge).
Why are we concerned?
False-brome is known to form dense patches along disturbed areas (roads, streams) which then spread seed into undisturbed forest. False-brome infestations can lead to:
- Reduced plant and animal diversity as other species are displaced
- Reduced ability to replace adult trees as seedlings fail to mature
How does it spread?
False-brome is spread only by seed, not fragments. False-brome seeds are moved around by:
- Tires and machinery
- Hiking boots
- Running water
What does it look like?
False-brome is a grass species that grows in thick bunches that get up to 3 feet tall. It has unusually bright green leaves which stay green into November or even later; these leaves are also known for their softness and fuzziness. Seeds and flowers are attached directly to the main stem, unlike true bromes, which have secondary stalks.
Are there lookalikes?
Grasses are considered a difficult group of plants to identify, and incorrect reports of false-brome are common even among professionals. When taken together, the characteristics mentioned above (fuzzy leaves, seeds directly attached to the main stem, and bright green bunches of foliage) are good indicators, though consulting the city or other weed management partners is advisable.
How do we deal with it?
- Manual: Digging up false-brome is simple but requires removal of all roots. Cutting flowerheads in June removes the possibility of seed spread. Excavated plants and cut flowerheads must be bagged and put in the garbage to prevent spread to new areas.
- Herbicide: Low rates of herbicide applied in fall will kill adult plants, though herbicide is most effective after a June flower cutting and followed by annual monitoring for new seedlings.
How can folks help?
If you think you’ve found false-brome, call either the City of Portland or contact the Oregon Department of Agriculture. Several grass species are commonly misidentified as false-brome; there should be positive identification before management is attempted.