Ludwigia peploides is an aquatic plant from South America — but volunteers and state workers spent most of Wednesday yanking it out of the Peconic River in Calverton.

The species, also called floating primrose-willow, is invasive, meaning it is a nonnative visitor that takes root in an ecosystem and poses a threat to the native wildlife, said Chart Guthrie, state Department of Environmental Conservation regional fisheries manager.

Nearly 25 DEC staff members and volunteers patrolled the water near the Edwards Avenue Dam in kayaks, canoes and flat-bottomed jon boats, pulling up the Ludwigia from onboard the crafts and wading into the water to access thicker areas.

The uprooted plants, which cannot grow out of water, will be deposited near the dam and later composted on DEC property.

Ludwigia is a bright green plant with several shiny, oval-shaped leaves extending from a central stem. It grows in clumps and blooms vivid yellow flowers that resemble a buttercup.

Because the plant’s leaves extend above the water, it “chokes out” sunlight and deprives underwater life of oxygen, said Sarah Schaefer, Suffolk County program coordinator for the Peconic Estuary Program, which partners with the DEC to clean up the river.

This could cause a disruption in the ecosystem that would harm native plants, fish and other aquatic organisms, Schaefer said.

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“That’s really our focus,” she said, “trying to get more native conditions and improving the habitat.”

Ludwigia was first documented in the Peconic River in 2003, and the DEC has been doing hand removal since 2006, Guthrie said.

The plant can form thick mats, Guthrie said, and can impede boats and recreational vehicles as well.

It is unclear exactly how Ludwigia first made its way into the Peconic, but one way could have been through homeowners planting it in their backyard ponds and water gardens, Guthrie said — allowing the “pretty plant” to spread beyond South America.

And because Ludwigia is not native, it is not controlled by the same predators and parasites that would check its growth in a native environment, Guthrie said.

“It kind of has an unfair advantage,” he said.

Volunteer groups weed parts of the Peconic River area between two and four times a year, Guthrie said. Wednesday was one of two large-scale efforts to pull the weed this month, Guthrie said.

“I don’t think we’ll ever eradicate it,” he said, “but I think we can keep ahead of it.”