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Gardening hangovers, Part 4: acacia

April 22, 2010 |  7:05 am
Invasive_Acacia On a recent morning, a northern harrier — a large raptor — spirals up into the blue over Ballona Wetlands, until it looks as if it’s gliding over the snowcapped San Gabriel Mountains in the distance.

For the harrier and some other animals, Ballona is one of the few — if not the only -- habitable spots remaining in coastal L.A. County.  Many of these species, including the endangered Belding’s savannah sparrow and the county’s last burrowing owl, need low-growing habitat such as pickleweed or native dune flowers (silvery leafed lupine, beach evening primrose).

Volunteers have restored some of the native vegetation at this 600-acre degraded wetland near Playa del Rey, but Ballona still hosts a who’s-who of aggressive exotic plants known as invasives: ice plant, pampas grass, Brazilian pepper tree, myoporum, eucalyptus and various acacias. These plants hamper restoration efforts on a parcel the state spent millions to acquire.

Conservation biologist Dan Cooper points out one of the acacias. It “probably has some nutritional value, but the main birds that feed upon it are nonnative pest species like starlings.”  The seeds survive digestion and sprout up in thick clumps. “It’s changed the habitat from being open, which a burrowing owl would like, to being basically a thick hedgerow which it can’t use.”

The nonprofit California Invasive Plant Council advises gardeners to pass on four weedy acacias — cyclops, longifolia, decurrens, and baileyana.

At least eight more of the 1,200 species of acacia have naturalized in California wildlands. They’re not widespread now, but many invasive plants lie low for years before running amok. And horticulturists continue to offer new acacia selections.

Often called wattles, acacias are common in parts of Australia, with a climate similar to California’s, so many are likely to thrive here. "The very plants we promote for saving water in gardens, which are often the Mediterranean-climate plants, in some cases have the greatest potential for being invasive,” says Jim Folsom, director of botanical gardens at the Huntington. He notes that thirsty tropical plants are less likely to invade Southern California wildlands.

The acacias and other exotic plants at Ballona have advocates who point out that some native animals use them. For Cooper, that’s analogous to feeding kids candy because they like it. “Just because a species uses something doesn’t mean it’s good for the species or something we want around,” he says. 

California flora are rich in evergreen shrubs, so water-conscious gardeners can choose from several alternatives, including coffeeberry, lemonade berry, and holly-leaf cherry. An exotic shrub that stays put is pineapple guava, which produces showy, edible flowers and fruits with a minty-pineapple flavor.

-- Ilsa Setziol

Coming Friday: Scotch and Spanish broom

Photo: Acacia longifolia

Credit: Genaro Molina / Los Angeles Times

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