9/16/2023 0 Comments French broom plant![]() It burns readily and carries fire to the tree canopy layer, increasing both the frequency and intensity of fires. French broom is believed to be responsible for reducing arthropod populations by one-third in Golden Gate National Recreation Area (Lanford and Nelson 1992). Infestations of broom degrade the quality of habitat for wildlife by displacing native forage species and changing microclimate conditions at soil levels. ![]() Foliage can cause digestive disorders in horses (Parsons 1992). In some livestock, ingestion of plant parts can cause staggering followed by paralysis (McClintock 1985). Since it can grow more rapidly than most trees used in forestry, it shades out tree seedlings in areas that are revegetated after harvest.įrench broom foliage and seeds are toxic, containing a variety of quinolizidine alkaloids, especially in young leaves (Montlor et al. In an experiment in New Zealand 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 (141 cm) in two growing seasons. It is a strong competitor and can dominate a plant community, forming dense monospecific stands. It displaces native plant and forage species, and makes reforestation difficult. WHAT PROBLEMS DOES IT CAUSE? French broom currently occupies approximately 100,000 acres in California (D. It resprouts readily from the root crown after cutting, freezing, and sometimes after fire (Bossard et al. observation), in mud, and on road grading or maintenance machinery (Parsons 1992). After pods open explosively, flinging seeds up to 4 m, the seeds are further dispersed by ants, birds, and animals and in river water and rain wash (McClintock, pers. A medium-sized shrub can produce over 8,000 seeds a year (Bossard unpubl. It spreads via prodigious seed production. WHERE DID IT COME FROM AND HOW IS IT SPREAD? Native to countries surrounding the Mediterranean and in the Azores, French broom is thought to have been introduced to the San Francisco Bay Area in the mid-1800s as an ornamental. French broom seedlings are less tolerant of frost than are those of Scotch broom and consequently are less often found at higher elevations. While Scotch broom is a problem species in many parts of the world, French broom is especially problematic in California and Australia (Partridge 1989, Parsons 1992). It is competitive in low-fertility soils because of mutualistic relationships with nitrogen-fixing bacteria found in small nodules on roots. Unlike other broom species in California, it grows reasonably well on alkaline soils with pH 8. It is found growing in varied soil moisture conditions, but prefers siliceous soils. This broom is common on coastal plains, mountain slopes, and in disturbed places such as river banks, road cuts, and forest clearcuts, but it can colonize grassland and open canopy forest. It is also known from Del Norte County, northern Sierra Nevada foothill counties to 800 meters, and in Kern, San Bernardino, and San Diego counties. WHERE WOULD I FIND IT? French broom is found primarily in central coastal counties from Monterey County north to Mendocino County and inland in Lake, Solano, and Contra Costa counties. Seeds: 3-8 seeds per pod, brown to black, shiny, round to oval, with a cream to yellow eliaosome. Fruit: a pod, 0.5-1 in (15-25 mm), covered in dense silky hairs, dark brown or black at maturity. (1-3 mm).įlowers: shaped like pea flowers calyx silky-hairy, 0.2-0.3 in (5-7 mm) banner 0.3-0.5 in (10-15 mm), corolla yellow to light yellow. Inflorescence: 4-10 flowers in subcapitate racemes (on axillary short shoots) terminal or central flower usually opening last pedicels <0.1 in. Leaves: alternate stipules <0.1 in (2 mm) deciduous leaflets of trifoliate leaves 0.3-0.5 in (10-15mm), oblanceolate to obovate with length about twice width, upper surface glabrous, lower surface with appressed or spreading hairs hairiness petioles <2 in. Shrub, usually <10 ft (3 m), but occasionally to 16 ft (5 m). This species sometimes is confused with Scotch broom (Cytisus scoparius), which has pods with hairs only at the seam, green stems that are five-angled and ridged, flowers that are golden yellow and larger than half an inch, and only about fifty-five percent of total green tissue as leaves (Bossard and Rejmánek 1994).ĭescription: Fabaceae. The mostly inch-long pods are covered with hairs. The small (less than half-inch) yellow flowers are pea-like and clustered in groups of four to ten. About eighty-five percent of the photosynthetic tissue of French broom is in leaf tissue. The round stems are covered with silvery, silky hair, and the small leaves are usually arranged in groups of three. Distinctive features: French broom ( Genista monspessulana) is an upright, evergreen shrub, commonly to ten feet tall.
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