Scotch broom in Washington and Oregon: how to identify it and get rid of it

This is the full Scotch broom guide; the site’s brush clearing guide sets it beside Himalayan blackberry, English ivy and holly. On a big lot or a slope, broom work becomes part of land clearing in Washington and Oregon, with its own permit and debris rules.

The Washington State Noxious Weed Control Board finds it on roadsides, pastures, grasslands, open areas and freshly disturbed soil. The Oregon Department of Agriculture (ODA) says it is found throughout western Oregon, with occasional isolated populations in the pine forests of eastern Oregon.

How to identify Scotch broom and its look-alikes

Scotch broom is a many-branched shrub 3 to 10 feet tall. Young branches are green with five hairy ridges; the few leaves are small, the upper ones single and the lower ones in threes, and they often drop early. The bright yellow flowers are about ¾ inch long and turn into flat, brown-black pods with hairy edges (weed board). ODA says it blooms in May and each pod holds up to a dozen seeds.

Sources: Washington State Noxious Weed Control Board species pages; ODA Scotch broom profile, noxious weed profiles and Noxious Weed Policy and Classification (2025); all checked 2026-10-02.

In Washington, the two look-alikes matter more than their numbers suggest. Washington lists French and Spanish broom as Class A weeds, and the weed board says eradication of all Class A plants is required by law; French broom has been found escaped in Washington only once, on the University of Washington campus in Seattle. If you think you have either one, call your county noxious weed board. Gorse is the easy one to tell apart: it has spines.

Is Scotch broom a noxious weed in Washington and Oregon?

Yes, in both states. Washington lists Scotch broom as a Class B noxious weed. Class B weeds are designated for mandatory control in regions where they are not yet widespread; where they are already abundant, control is decided locally, so your county weed board is the one to ask. King County, for example, requires control only on the I-90 right-of-way east of milepost 34 and on the Highway 2 right-of-way where it enters the county.

Selling it is another matter. Washington’s noxious weed seed and plant quarantine covers Scotch broom, French broom, Spanish broom and gorse. Oregon’s B list includes Scotch, French, Spanish and Portuguese broom and gorse, and its quarantine prohibits transporting, buying, selling, offering for sale or propagating them (OAR 603-052-1200). ODA also gives gorse and Portuguese broom a T designation, which marks B-list weeds it has selected as a focus for prevention and control.

Why Scotch broom matters: seeds, fire and forests

Broom’s power is its seed. King County says one plant can make up to 10,000 seeds a year, and its pods split open with an audible snap and throw seeds up to 20 feet; ODA says the dried pods crackle and pop in midsummer. How long that seed survives in the soil depends on whom you read:

Sources as named in each row, checked 2026-10-02.

Whatever the figure, a cleared patch keeps sprouting for years, and King County’s best management practices (BMP) guide says to watch for new plants for at least ten years after the first treatment and after any soil disturbance.

Broom also burns. The Forest Service review says dense stands create a serious fire hazard, and older stands are a mix of dead, partly dead and living plants. King County calls broom highly flammable and warns against leaving cut piles near forests or buildings. Near a home in wildfire country, clearing it belongs in your defensible space work.

On open land, the same review says broom threatens Oregon white oak woodlands in Washington and Oregon and is a serious pest in logged areas replanted with conifer seedlings. ODA says it smothers tree transplants, raising seedling deaths or slowing growth in their early years, and the Washington weed board lists the loss of grassland and open forest. ODA’s broom profile, which carries no date, puts control costs on Oregon timberlands at $47 million a year in labor and chemicals, plus lost productivity.

Is Scotch broom poisonous?

Yes, if eaten. King County’s BMP says the seeds and other plant parts are toxic to humans, horses and livestock, and the weed board warns that the seeds are toxic to livestock and horses. North Carolina State Extension’s plant database rates its poison severity as high, names quinolizidine alkaloids in the leaves, seeds and stems, and lists vomiting, excitement, muscular weakness and convulsions as symptoms. If a child eats any, call Poison Control at 1-800-222-1222; for a pet or horse, call a veterinarian. ODA adds that broom pollen can be an allergen for allergy sufferers during bloom.

How to get rid of Scotch broom

Scotch broom removal is mostly about size and season: pull what you can, cut what you can’t, and keep the seed from traveling. The steps follow King County’s BMP and the Washington weed board.

1. Pull the small onesSeedlings and plants up to about 1 inch thick pull out by hand from fall through spring, when the soil is moist (King County BMP). King County’s web page puts the hand-pull limit at plants under 3 feet.
2. Lever out medium plantsA Weed Wrench, Extractigator or Uprooter pries the plant out with its roots (weed board).
3. Disturb as little soil as you canThe weed board warns that levering plants out can trigger a flush of seedlings from the seed bank.
4. Cut the big ones in the droughtCut plants with stems over 2 inches as close to the ground as possible in late July and August (King County BMP; weed board). Brown, mature stems respond best; green ones are more likely to regrow (King County).
5. Mow to stop seed, not to killMowing several times a season for several seasons keeps broom from setting seed, but King County says it is unlikely to kill it all, especially young plants.
6. Plant something elseNative plants suited to the site cut re-infestation; in grass, a healthy grass and clover mix resists broom (King County BMP).
7. Check every yearPull new seedlings for at least ten years (King County BMP).

Insects help in the background. ODA says three approved biological control agents, a beetle, a seed weevil and a twig miner, are established in Oregon and can significantly cut seed production and shorten a broom plant’s life; the Washington weed board lists two seed-feeding weevils.

When to pull, cut or mow Scotch broom

Sources: King County Scotch broom BMP (2008) and web page; ODA Scotch broom profile; Washington State Noxious Weed Control Board; checked 2026-10-02.

Late July and August is when broom is thirstiest because it is when the west side is driest. NOAA’s 1991–2020 normals put July and August together at 0.57 inch in Medford to 2.19 inches in Everett, against 5.2 to 8.2 inches in November alone in every one of these cities but Medford.

Scotch broom seeds: disposal without spreading them

Every plant that leaves the ground with ripe pods is a seed shipment. King County’s rules of thumb:

Most people in town can’t burn it. In Washington, residential and land-clearing burning is not allowed in urban growth areas or in cities over 10,000 people (WAC 173-425-040), and Oregon DEQ says bans depend on where you live, with cities, counties and fire districts adding their own. Check Washington yard debris burning rules or Oregon yard debris burning rules first.

Hauling is covered in Washington, where the quarantine exempts taking broom to a landfill or other disposal under a weed agency’s guidelines (WAC 16-752-630). Oregon’s quarantine rule lists transport among its prohibitions and its text has no disposal exception, so in Oregon ask your hauler or county weed program how they want broom delivered.

When to bring in a crew

A thick stand on a slope, along a long fence line or across an acre is more cutting and hauling than most people can do in one August. On steep ground, King County’s BMP says to replant with plants of varying root depth to hold the slope. Brush clearing is priced by the hour; this site models a three-person crew at about $225 per crew-hour in Oregon and $210 in Washington (modeled estimate, not quotes; method). Ask whether the quote covers bagging pod-laden plants and a return visit for seedlings. The permit side of bigger jobs is on the land clearing hub.

Broom rarely grows alone. Where it shares a lot with Himalayan blackberry or ivy climbing the trees (see English ivy on trees), plan one clearing and one follow-up schedule for all of it.