What’s lurking at Upper Newport Bay? Invasive knapweed, and it’s got to go

Conservation groups are ramping up efforts to eradicate an invasive plant known as Moroccan knapweed from Upper Newport Bay after it was found in the Big Canyon area last month.

Such plants can disrupt the area’s ecology, quickly growing in number and pushing out plants that sustain native insects and animals, said Ron Vanderhoff, a member of the Orange County chapter of the California Native Plant Society.

“When that happens, it begins diminishing the pollinators, reptiles and herbivores,” Vanderhoff said. “Everything starts coming apart, and other plants begin disappearing.”

When walking though the lush foliage of Upper Newport Bay, it’s often easy to miss a plant or two that are out of place among the native vegetation.

But invasive plants have posed a problem in the area for decades. Conservation groups such as the Native Plant Society, Back Bay Conservancy and Irvine Ranch Conservancy have been keeping an eye out for non-native greenery in recent years.

A member of the Native Plant Society was hiking at the bay late last month when she saw an unfamiliar plant. She took photos and sent her findings to Vanderhoff, who began investigating.

They eventually identified the plant as Moroccan knapweed, an herb that is native to the Canary Islands, a Spanish archipelago just off the southern coast of Morocco, according to the U.S. Department of Agriculture.

About 500 to 1,000 Moroccan knapweed plants were found at Upper Newport Bay, also known as the Back Bay. Vanderhoff estimates the species was introduced to the area two or three years ago.

Members of the Irvine Ranch Conservancy removed the plants from the Back Bay on Wednesday and Thursday, but that doesn’t mean all traces are gone.

“Even though the plants have been removed, the seeds are still present. There are certainly going to be a lot of seeds sprouting,” Vanderhoff said. “It’s going to take several years of regular monitoring before we can hopefully declare it eradicated.”

Moroccan knapweed was first recorded in the United States in 2010 at Anza Borrego State Park near Borrego Springs northeast of San Diego. Since then, more than 10,000 of the plants have been found in the park. Crews have been working to remove the species for the past four years but have not succeeded.

The herb, a member of the sunflower family, can grow quickly to shrub size and in one season can release about 2,500 seeds.

Invasive plants like Moroccan knapweed are adaptable to new habitats, grow aggressively and have high reproductive capacity, according to the National Invasive Species Information Center.

“They didn’t evolve here with the other plants and organisms that are present, so they don’t have any natural enemies,” Vanderhoff said. “The insects aren’t evolved to keep them under control. Frequently they have a competitive advantage against other plants that have these checks and balances in place.”

People often unknowingly take invasive species from place to place on their clothing or shoes or in cars, Vanderhoff said. Sometimes birds carry the seeds to new locations, he said.