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French Broom (Genista monspessulana)

Pea or Bean Family (Fabaceae)

Genista monspessulana (french broom).  Photo by BLM.
Photo: BLM

       Genista monspessulana (french broom).  Photo by BLM.      
Photo: BLM

Genista monspessulana (french broom).  Photo courtesy of calphotos.berkeley.edu
Photo: calphotos.berkeley.edu

Description/Habitat:  French broom (Genista monspessulana) is an evergreen shrub that can grow up to 10 feet tall.  It is native to the Mediterranean region and Azores Islands, inhabiting humid and sub-humid areas in its native range. French broom currently occupies over 100,000 acres in California.
Leaves:  Stems are typically leafy and usually moderately to densely covered with silky, silvery hairs. Leaves are alternate, and compound with 3 leaflets. Leaflets are oblong to ovate, mostly 10-20 mm long, upper and lower surface sparse to densely covered with appressed, short, silvery hairs.
Flowers:  Flowers are pea-like, usually bright yellow, and clustered in groups of four to ten. They are located at the ends of short axillary branchlets. Flower size is roughly 1 cm long. During the flowering season, the plant can be slightly fragrant.
Seeds:  Seedpods are brown at maturity, slightly flattened, 1-3 cm long, ± 0.5 cm wide, densely covered with appressed, long, silky, silvery to reddish gold hairs. There are about 5-8 seeds per pod, and are on average ovoid, shiny, smooth, black, and about 2-3 mm long. A medium-sized shrub can produce over 8,000 seeds a year, and disperse seeds up to 13 feet and beyond. The seeds are hard-coated and long-lived (30+ years) under field conditions.
Flowering Period:  March through May inland, and March through July along the coast. Seeds germinate after the first rains in the fall through early summer in inland areas, and from winter through mid-summer in coastal regions, depending upon weather conditions. Seeds mature June through July.
Management:  The preferred removal method on Fort Ord National Monument is to manually pull them. The entire plant and root system must be removed in order to prevent resprout from the base. Cutting the plant off at the base will not kill it as it readily resprouts. Do not allow these plants to go to seed as they have a persistent seed bank that will require subsequent treatments over many years.

During the rainy season, typically from early January to April, French broom seedlings can be killed with the use of high-temperature flaming equipment, such as a blowtorch or roofing torch. This method does not burn the plant seedlings, but instead it ruptures the cell walls causing the plant to wilt, exhausting the remaining resources used for re-germination.  This technique is only used when there has been significant rain fall for the season, and there is moisture on the plants to prevent spot fires from occurring.
Herbicide treatments of glyphosate (cut-stem and foliar applications) are effective but sometimes require multiple treatments. Foliar herbicide treatments are often used on the Army range areas where unexploded ordnance is an issue.

Bossard, C. 2000. Cortaderia jubata. Pp. 203-207 in Bossard, C. C., J.M. Randall, and M. C. Hoshovsky. Invasive Plants of California's Wildlands. University of California Press. Berkeley, CA.

DiTomaso, J. M. and E. A. Healy. 2007. Weeds of California and Other Western States. Volume 1: Aizoaceae to Fabaceae. University of California Department of Agriculture and Natural Resources: 752-762

Last updated: 08-20-2012