French broom (Genista monspessulana) is an upright, evergreen shrub native to the Azores and countries surrounding the Mediterranean Sea.
In North America the invasive shrub occurs from southern British Columbia south to southern California (USFS). French broom is thought to have been introduced to the San Francisco Bay Area in the mid-1800s as an ornamental. The plant is about ten feet tall and spreads by seed, with a medium-sized shrub producing 8,000 seeds a year (Calif. IPC).
French broom currently occupies approximately 100,000 acres in California (Calif. IPC.). It displaces native plant and forage species, and makes reforestation difficult. It can dominate a plant community, forming dense monospecific stands. In studies, French broom had a higher growth rate than any other broom species found in California, reaching an average height of more than 4.5 feet in two growing seasons. French broom foliage and seeds contain a variety of toxic alkaloids, especially in young leaves. In some livestock, ingestion of plant parts can cause staggering followed by paralysis. Foliage can also cause digestive disorders in horses. Infestations of broom degrade the quality of habitat for wildlife by displacing native forage species and changing microclimate conditions at soil levels.
French broom is classified as a noxious weed in California, Hawaii, and Oregon.
Resources and Additional information:
- California Invasive Plant Council: http://www.cal-ipc.org
- USDA FS: http://www.fs.fed.us/database/feis/plants/shrub/genmon/all.html