French broom (Genista monspessulana)
Legume family (Fabaceae)
Photo courtesy of Brother Alfred Brousseau, St.Mary's College of California
Description: French broom is an evergreen shrub up to ten feet tall. The round stems are covered with silvery, silky hair, and the small and alternate leaves are usually arranged in groups of three. The small (less than half-inch) yellow flowers are pea-like and clustered in groups of four to ten. The mostly inch-long pods are covered with hairs.
This species is sometimes confused with Scotch broom (Cytisus scoparious) which has pods with hairs only at the seam, green stems that are five-angled and ridged, and flowers that are golden yellow and larger than half an inch.
Habitat: French broom readily colonizes open grasslands, coastal plains, mountain slopes, and disturbed areas such as river banks, road cuts, and managed forest areas. It grows in varied soil moisture conditions, and can tolerate fairly alkaline soils with a pH 8. It is competitive on low-fertility soils because of its nitrogen fixing bacteria found in small nodules on roots. It is generally found below elevations of 2625 feet as it is not a fan of frost.
Distribution: Native to countries surrounding the Mediterranean and in the Azores, French broom is distributed globally. It occupies over 100,000 acres in California. It was thought to have been introduced to the San Francisco Bay area in the mid-1800's as an ornamental. It produces large amounts of seed. A medium-sized shrub can produce over 8,000 seeds a year. Pods open explosively, flinging seeds up to and farther than 13 feet.
Flowering period: French broom flowers March through May inland, and March through July on the coast. Seeds mature June through July.
Eradication note: Manually pull these plants prior to seeding or flowering. For large infestations, a Weed Wrench™ is recommended. Do not allow these plants to seed as they have a persistent seed bank that will require subsequent treatments. Cutting the plant off at the base will not kill it as is readily resprouts. The entire plant with root system must be pulled.
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