War on Weeds—weeds are everybody’s problem

THE ISSUE:  Scotch broom

  Scotch broom (Cytisus scoparius) is a perennial shrub native to northern Africa and parts of Europe. It was introduced into the U.S. in the 1850’s as an ornamental, later it was used for erosion control. It invades roadsides, pastures, and other disturbed sites. Scotch broom is unpalatable and can be toxic to livestock.

Scotch broom can grow 3-10 feet tall. Leaves are small oblong, pointed and grow in groups of three. It is well known for its bright yellow flowers that look like ‘pea’ flowers. Seed pods are hairy and green when young, as they mature, they turn black to brown. When ripe they explode, launching the shiny greenish-brown-black seeds. Seeds can remain viable in the soil for up to 30 years. Scotch broom has special characteristics that enable it to outcompete native species. It loses its leaves under dry conditions, but stem tissue can perform photosynthesis helping it to thrive under adverse conditions. It also forms a symbiotic relationship with nitrogen fixing bacteria allowing it to prosper in nitrogen depleted soils.

Integrated Pest Management (IPM) Options: 

• Prevention— Learn to identify this plant. Never transport unknown plant material. Always plant clean seed! 

• Mechanical—Mowing plants at the end of the summer can help reduce scotch broom populations if done regularly. Do not try to remove this plant by digging soil disruption will allow more plants to germinate.

• Cultural—Establish healthy stands of desirable vegetation that will compete with scotch broom. Reduce disturbance and use proper grazing techniques. 

• Biological—Scotch broom bruchid (Bruchidius villous) and scotch broom seed weevil (Exapion fuscirostre) are both larvae that cause damage to developing scotch broom seeds. 

• Chemical— There are several herbicide options available to use on this weed species. For more information on products and rates visit: https://pnwhandbooks.org/weed. Then search “broom”. Then select “broom, scotch”.  Always read and follow herbicide label directions!

Justin Hatch, University of Idaho Extension Agriculture Educator in Caribou and Bear Lake Counties.
208-547-3205 [email protected]