The Problem French broom, Scotch broom, Spanish broom, Portuguese broom, and gorse are all shrubs native to central and southern Europe that are impacting millions of acres in California and western North America. Infested forest lands result in higher regeneration costs after harvest of timber, increased risk of wildfire, and reductions in sight safety distance along access roads. Infested pastures and meadows result in reduced forage for livestock and wildlife due to the high levels of poisonous quinolizidine alkaloids in their leaves and stems. Dense stands of these leguminous shrubs prevent establishment of native and desirable plant species, especially after fires where their ability to fix nitrogen allows these exotic weeds to out compete and exclude native chaparral species. The seed bank in the soil commonly ranges from 30,000 to 100,000 seeds per square meter and seeds remain viable for many years.
Brooms present an increased fire hazard and thus are a serious threat to homes.
Millions of dollars in control costs are spent annually against these invasive exotic weeds by public and private landowners. In California, infested areas occur in the Sierra Nevada foothills and the western side of the Coast Range. Over the last decade, they have extended their range and increased in density in established areas. This same trend has been observed for the other brooms and gorse. The genera to which these exotic brooms and gorse belong are closely related and weakly differentiated.