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No retreat, it's time to battle 'The broom' | Guest Column
By Kate Yturri, Judy Winer, Gwen Stamm
Scotch Broom (Cytisus scoparius) is an invasive, many-branched shrub with green stems and bright yellow flowers, typically blooming from April to June and visible to us all from county roads.
It is classified as a Class B noxious weed in Washington state and control is required, because it is a serious fire hazard and is crowding out native and beneficial plants, causing loss of grasslands and degrading open space. Seeds are toxic to livestock and horses, and can remain viable for up to 80 years.
Now is a good time to remove Scotch Broom, before the pods mature to produce additional seeds.
Broom is easily identified by its 5-angled stems, small deciduous leaves (each with three narrow leaflets), and, of course, by the bright yellow flowers, each about 3/4-inch long with five petals. A similar looking shrub, gorse (Ulex europaeus) also is designated for control countywide and is distinguished by round stems and prominent spines on mature stems, instead of leaves.
Since one small foothold can infest an entire neighborhood, many of us volunteer to help our neighbors control infestations. There are several approaches for removal of Scotch Broom:
— Pull it out. For large brooms, we can borrow a weed wrench (for free) from the County Noxious Weed Control Program at the Senior Center on Orcas, the Land Bank office on San Juan, or from the county Public Works Department on Lopez.
— Cut it back to the ground each year before it sets seed. It is important to act before the small pods mature, in late June. Cutting mature plants greater than one inch at the base has shown to be the best technique to kill the plant, as it minimizes soil disturbance, thus doing less damage to desirable plants and bringing fewer seeds to the surface where they germinate.
Cutting is most effective when plants are stressed by summer drought and have had their energy sapped by flower production.
Monitor for seedlings each spring and pull them up, roots and all, while they are small and the ground is still moist. Since Scotch broom seed lasts for years in the soil, we must continue to monitor to prevent re-invasion by new seedlings.
Soil that is contaminated with Scotch Broom seeds should not be transported, and moving shrubs with mature seeds may cause further spread. Re-vegetation with competitive native trees and shrubs, and native grass mixes, can help prevent new infestations.
Cut or pulled broom without mature seeds can be left on site to decompose, or it can be chipped or burned if permissible. Transfer stations do accept broom for disposal but may charge a fee.
— Editor's note: the above authors are 2013 graduates of the WSU Master Gardener Program.