Environment & Science

Bad Seeds, Part 1 - Invasive plants harm native plants, animals

Fountain grass spreading across rare dune habitat in Point Mugu State Park.
Fountain grass spreading across rare dune habitat in Point Mugu State Park.
Ilsa Setziol/KPCC

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A variety of non-native plants are favorites of Southern Californians who prefer hardy species in their gardens. But a number of these popular plants are a major menace to some of the region's native plant and animal life.

The problem is visible in a variety of places, such as Point Mugu State Park. Straddling the coast between Los Angeles and Ventura counties, Point Mugu is one of the jewels of the California State Park system.

It is home to some of the world’s rarest habitats. But invasive plants – including fountain grass – are threatening those habitats.

Kneeling on a sand dune next to the Pacific Coast Highway, National Park Service ecologist Christy Brigham shows how fountain grass is threatening the butter-yellow flowers of beach evening primrose, dune verbena and other low-growing plants.

"You can see the invading hordes right on the horizon," says Brigham. A swath of fountain grass is moving down a hill towards Brigham.

"Where the fountain grass is very dense you can see there’s nothing else in there," she says. "It's overtaking this habitat."

Native to north Africa, fountain grass is a billowy garden plant topped with plumes resembling little foxtails. In California, its seed blows out of gardens and hightails into wildlands. And fountain grass is content to rough it in even the most forbidding places, such as dry rock faces.

Fountain grass disrupts animal life as well. As Brigham combs through dense thickets of fountain grass, she doesn’t spot a single insect.

While native plants offer local insects a rich menu of pollen and nectar, fountain grass flowers have "nothing" to offer, says Brigham. "The pollen they produce is of low quality." She notes that the flowers "don't look browsed at all," which points out another problem –"animals don't eat them, and that makes them even better able to survive."

Fountain grass also makes wildlands more fire-prone. It helps fires ignite and spread more easily in the state’s unique and vanishing sage scrub habitats.

"And then because the grasses recover much quicker and more successfully than shrubs you get repeat fires," according to invasive plant expert Carl Bell. "Over time, that eliminates most of the coastal sage scrub species and you wind up with a grassland."

Some 300 non-native plants have taken root in the Santa Monica Mountains. Most settle in discreetly; Brigham says about 20 are causing significant problems.

Eradicating invasive plants is labor intensive – it can take years of repeat weeding and careful application of pesticides. The state doesn't have nearly enough money to do a thorough job.

Doug Johnson of the non-profit California Invasive Plant Council estimates park agencies spend more than $80 million a year just to keep some of the worst weeds in check.

"The work being done on invasive plants is really a drop in the bucket of what needs to be done," says Johnson.

Many scientists say invasive plants are the number two threat to California wildlands – second only to outright habitat destruction. And yet fountain grass, ice plant, periwinkle and a couple dozen other invasive plants are readily available – they’re for sale at local nurseries.