In any case, complete control of broom in Claremont Canyon is definitely possible. The exact removal techniques will differ depending on the location of the broom colony, the extent of financial and public support for broom removal, the advantages of the season, and the depth of commitment to the goal of elimination, which is to say the amount of follow-up. Working outward from these areas, the last places to be treated would be colonies in areas likely to be invaded by other weeds when the broom is eliminated. Concentrate on removing broom first from the most pristine areas-those outliers that could become a serious broom colony that will threaten native flora.
With survey information clearly in hand, a strategy can be constructed using triage as the operative principle-identify what needs to be saved first and leave for last that which is least likely to succeed. In a relatively small area like Claremont Canyon, such survey work could be done by direct observation or more sophisticated data-based methods. The first step is to survey the land and create an inventory of flora and its location so that, for example, outliers might be identified, threatened sensitive habitat might be located, areas of mixed vegetation might be distinguished, and places where broom seed might spread downhill could be flagged. The basic strategy for success proceeds from a clear understanding of both native flora and broom. Since then, what little attention has been paid to the broom invasion hasĪged to halt the advance of broom and to suppress the vitality of the seed bed, even as broom is expanding in directly adjacent public areas. French and Scotch broom were included but not prioritized. The “Vegetation Management Almanac in the East Bay Hills,” published in the 1990s by our local Hills Emergency Forum, illustrated 38 native plants, weeds, and invasive exotics. Casual or occasional trimming or extracting does nothing to arrest the advance of broom.
This plant’s arsenal is impressive and requires a response that is both deliberate and long term. Seeds can survive more than 40 years and are not destroyed by fire, enhancing broom’s aggressive potential. Cutting the plant off at the root only intensifies the root structure pulling up or weed-wrenching disturbs the soil so that nearby seeds tend to sprout.
Once even minimally established, broom begins an insidious process of capturing nitrogen from the air and setting it in the soil, making the soil too rich for most native species-but very inviting to other invasives. Thriving on recently disturbed soil, broom seeds easily take root.
French broom free#
Possessed of extraordinarily aggressive traits, French broom (Genista monspessulana) long ago escaped urban gardens and found free range in the wildlands of the west coast. IF YOU CONSIDER THE SUBSTANTIAL ADVANCES made by French broom in Claremont Canyon over the past decade, John Burroughs’ invective against the weeds of autumn might come to mind: “They are all outlaws every man’s hand is against them yet how surely they hold their own!”
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