Scotch Broom lines most of the roads into Coos Bay in spring and early summer. And, it seems, many visitors can hardly wait to get into town and ask, “what are those glorious yellow flowers and where can I buy some?”

Not so fast.

Jon Souder, executive director of the Coos Watershed Association and a great foe of the plant, said that his own mother admired it until he set her straight.

“It's an invasive weed, Mom,” he said. “You do not want it back home.”

Souder knows from long experience that introducing a plant from one area into another should be done with care. Plant and wildlife evolve over millennia into balanced systems of growth and control. Transferring an organism from an environment in which it has natural predators into one where nothing eats it can lead to ecological disaster. Himalayan blackberries, starlings, English ivy, Northern pike, and French snails are just a few misguided introductions.

How it got here

Scotch Broom, Cytisus scoparius, is another. It's a European member of the large, diverse pea family that found its home in the Pacific Northwest, when a Scotsman planted seeds on Vancouver Island in 1850, according to Jim Pojar and Andy MacKinnon in their book “Plants of the Pacific Northwest Coast.” Only three seeds germinated, but the descendants of those three plants have spread over hundreds of thousands of acres from Vancouver through California.

Originally, it was just a popular ornamental shrub for the garden. It grows 6 to 10 feet tall, with many slender, erect branches. It has tiny leaves with three leaflets. In spring and early summer, masses of bright yellow pea flowers bloom in the leaf axils. Light green seedpods follow, turning turn dark brown and hairy by late summer. On a hot day, if the air is still, you can hear them pop open and scatter the seeds, maybe 20 at a time. Some people consider it a lovely plant, yet the Oregon Department of Agriculture has declared it a noxious weed, one to be removed and controlled.

“It's because of the seeds,” explained Bruce Follansbee, an independent habitat restoration ecologist who works with Souder and other conservation groups, landowners, and land managers. “A mature plant can produce about 15,000 seeds a year. Most germinate within three to four years but about 30 percent stay viable in the soil for 20, 50, maybe 80 years. All legumes have this seed bank. It ensures their survival. It also means that you can never completely turn your back on areas you've cleared of broom.”

How it stays here

Like all members of the pea family, broom fixes nitrogen from the air and can live in extremely poor soil. It has a long taproot as well as lateral roots, making it very stable. These traits eventually made it the plant of choice for erosion control on road cuts. Its seeds clung to road-working equipment and fell off at other projects far away. Although sun-loving, broom doesn't invade forests, but it does line many a forest road. When an area is logged, broom is ready and waiting to colonize the bare land and seriously hamper the re-establishment of conifer seedlings.

Wherever broom germinates, it grows faster than most native seedlings and quickly deprives them of sun. Soon the bush is so dense nothing can grow near it. The following year brings more broom sprouts and fewer natives. Eventually the natives die out and any wildlife that used them for food or shelter moves on or dies out. Few creatures eat the broom's toxic seeds or sprouts, so the seed bank keeps building. Soon the wild and varied year-round natural beauty of an area is gone, replaced by one plant and its month and a half of spectacular flowers. Theresa Novak, writing for Oregon's Agricultural Progress Web site, describes this end result as “the ecological equivalent of a parking lot.”

Now's the time to strike

Broom flowers are looking bedraggled now, so now is the time to consider removing the bushes. Beware of some common mistakes. Chopping down the bush or mowing seedlings when the ground is moist will only encourage them to re-sprout, so wait until they are knocked out by drought. Don't dig them out. There are thousands of seeds in the soil waiting to sprout when the soil is disturbed. The best way to eradicate broom is with Weed Wrenches� (see sidebar). They lever the bush out quite easily, taproot and all, disturbing very little soil. Some seeds will inevitably sprout and need to be hand-pulled, but it's an easy job when the ground is moist.

The cleared land should be planted immediately with strong natives that will shade the broom seedlings, thus out-competing them. It should be monitored and all seedlings removed. This is what should be done on any cleared space whether burned, logged, bulldozed or treated with herbicides.

Alternatives

Souder recommends broadcasting wildflower seed on slopes and parking strips. If you have creeks, plant moisture-loving plants such as red osier dogwood, wax myrtle, small conifers, crabapples and elderberry. Elsewhere, plant other (almost) care-free native plants and reap a year's worth of colorful flowers, fruits, leaves, and even branches. Few are as showy as Scotch Broom but, close up and en masse, they are offer color and variety.

How can you help?

Remove Cytisus scoparius from your property and plant only non-invasive cultivars and natives. Watch this paper for public service announcements about conservation activities with groups like SOLV, SEA, the U.S. Bureau of Land Management, Coos Watershed, Audubon Society, and the South Slough National Estuarine Research Reserve.

(Master Gardener Valerie Cooley lives in Eastside and enjoys baby-sitting her two granddaughters, birdwatching, kayaking, gardening and hiking.)