Question: As recent transplants to Oregon, we found the area below our home covered with the most beautiful green and yellow shrubbery. Now, our neighbors are telling us that it is a noxious weed that should be removed. Is it really that bad and, if so, what should we do to get rid of it?
Answer: You are not the first people to be infatuated with the beauty of Scotch broom. It was first imported to this country from Europe as a decorative shrub. When we discovered how effective it was in providing soil stabilization, we planted it on hillsides and alongside our roads.
Today, because of its ability to rapidly establish itself, Scotch broom and its cousins, Spanish, Portuguese and French brooms, as well as gorse, cost Oregonians about $40 million a year in control efforts and lost forestry production. So, yes, it is that bad, and you need to get rid of it.
One of the most effective removal methods for the small broom plants with stems up to 1/2 inch in diameter is called a weed wrench. It works by fastening to the base of the broom, and then using the lever to pull it out by the roots.
The reason we only recommend it for the smaller plants is that the root system on larger plants can be so big, it radically disturbs the soil and can uncover other broom seeds, which brings them to the surface and, in turn, allows them to germinate. Broom seeds can and do remain dormant in the soil for years.
In the July through September time frame, cutting can be most effective. You will want to avoid cutting if the plants are producing seed pods. The pods will fall off and be the basis for many years of future crops. Mowing works well, as repeated mowing weakens the plants but, once again, avoid mowing when the seed pods are ripe.
Chemicals will work to control your brooms. However, here are a few guidelines that you should remember. As long as the covered land is yours, you may treat it with chemicals. It is illegal to use chemicals on the land of others without their permission. If you are adjacent to public land, the person applying the chemicals must have either a public applicator’s or commercial applicator’s license.
Foliar sprays are best applied in the spring for two reasons: Mature plants are less susceptible to chemicals, and the cooler temperatures reduce the chance of chemical drift to neighbors’ properties. The sprays that are effective on the brooms, glyphosphate and imazapyr have no discretion on what they kill.
Whether it is from direct application or drift, the chemicals will kill any broadleaf plant they come in contact with. Avoid spraying when the plant is in bloom. The flowers actually protect the plant from full coverage and reduce the effectiveness of the spray.
Another effective way to apply the chemicals is the “cut stump” method. Cut the plant off low to the ground and, within a few minutes, paint the stump with your herbicide. The broom, not knowing that it has lost its upper foliage, will draw the chemicals down into the root system. Your chemicals will be applied directly to where they are needed, and you reduce waste and the chance of contamination to nearby plants.
With all chemical applications, be sure to read the label on the container prior to use; it is the contract that you are legally obligated to follow when you use the chemical.
First, be sure that the chemical you have purchased is for brooms. Then, follow the label to the letter for application, storage and disposal of the empty container. When the label calls for protective clothing, wear it. The effects on humans and animals may not be readily apparent but can be just as dangerous.
To dispose of the cut Scotch broom, first examine it to be sure there are no seed pods on the plant. If you have pulled it with a weed wrench, place the plant on a piece of canvas to avoid letting the roots come in contact with your soil. Cut Scotch broom can be dried or put through a shredder. The plant material, minus the seeds, is high in nitrogen, decomposes rapidly and is good for your soil.
We are sorry to have awakened you from your dream of a brilliant yellow and green landscape. The broom family is hearty and has a strong will to live. You should plan on several years of search-and-destroy efforts before the area will be under control.
As soon as the Scotch broom removal is started, the vacant space should be filled with another fast-growing, competitive native plant. If you desire trees, Douglas fir or red alder will provide a shady covering. For shrubs, consider Oregon Grape (our state flower), woods rose, currants or snow berry. Native grasses can also be planted to limit the bloom invasion.