I’m holding in my hand something that looks decidedly alien.

It’s small and greenish—let’s call it chartreuse—with rhizomes that extend, like tentacles or antennae, from a stem, reaching in vain for somewhere to take root.

Like something from a science fiction film, this 20-centimetre piece of aquatic matter has the ability to destroy a lake’s ecosystem before moving to surrounding waterbodies. And the more you try to kill it, the more determined it is to reproduce.

The species is, in fact, alien. To this lake anyway.

Yellow floating heart, a Japanese ornamental plant, was introduced to Seymour Lake, near Smithers, about 20 years ago by a resident who planted it along the shore outside their home. There it grew, in an isolated clump, for more than a decade until the home’s subsequent owner disturbed it while doing work along the shoreline.

That’s when Nymphoides peltata began to take over. Groupings began popping along the warmer, shallower southeast shore. Then they began to appear on the western shore. In 2012, former resident Allen Banner, then a regional forest ecologist with the BC government decided it was time to identify the plant.

He quickly realized they had a problem.

“This plant has reproduction down to a fine art,” Banner says. “It has the capacity to be transported to other lakes, which would be a terrible thing.”

When it comes to invasive plant species, northern BC has some reassuring advantages. To start with, we have fewer infestations. If residents are careful not to spread existing ones and quick to report new sightings, we’re more likely to stay on top of it. In addition, cooler temperatures in the region mean invasive plants are slower to spread.

That, of course, is changing with climate change.

Right now in our region, the invasive aquatic plants that pose the greatest concern are Seymour Lake’s yellow floating heart and flowering rush in Bouchie Lake near Quesnel, according to Denise McLean, an invasive plant specialist with the provincial government.

“Any aquatic species we have, we have issues with control,” McLean says. “We have fewer tools to be able to manage them.”

BC’s existing Weed Control Act was designed for agriculture. While it gives regional districts the ability to ticket the person responsible and recoup costs, enforcing it isn’t easy. Growing within lakes and streams, aquatic species exist on Crown land, which makes finding a perpetrator that much more difficult.

Penni Adams is the program manager for Northwest Invasive Plant Council. The organization focuses on terrestrial and riparian plants. She says Himalayan balsam, Japanese knotweed, yellow flag iris, and the common tansy are top of the council’s watch list.

“Those are the three we are concerned about because they are between water and dry land,” Adams says. Plants that take hold on lake shores and riverbanks not only contribute to erosion and degrade wildlife habitat, they easily spread when seeds and plant fragments drop into moving water.

Yellow floating heart reproduces both through fragments, which can take root, and seeds from its small yellow flowers. Until recently, Seymour Lake was the only known natural lake in the province where it existed, and one of its most northerly locations. In the Lower Mainland, Hatzic Lake was recently added to the list. VanDusen Gardens in Vancouver clears it from its manicured ponds every other year.

Invasive species are unpalatable to local herbivores and have no predators. As such, they begin to take over. The dense mat that yellow floating heart creates reduces light for fish and other plant species. Rotting biomass depletes the lake of oxygen. Its tendency to grow along the water’s edge makes the lake less accessible for boating and swimming.

The shoreline in front of Poppy Dubar’s home was cut less than a week earlier, yet small heart-shaped leaves are already appearing on the water’s surface. She launches her stand-up paddle board and glides onto the lake.

“I’ve become quite obsessive about it,” she says, kneeling to drag fistfuls of the weed onto her board.

The question of whether Seymour Lake will ever be rid of yellow floating heart is becoming increasingly discouraging. For the past three summers, members of the Seymour Lake Conservation Society, an organization formed in 2015 to address the problem, placed their hopes on a vacuum dredger—a barge with accompanying diver that would suck roots from the lakebed.

In August, residents learned that the idea had been canned. It seemed unlikely that the method, which is untested on the tenacious lily, would fully remove the plant’s extensive root network. For the time being, the society has hired two full-time summer students to cut the stems and remove the plants before they seed.

“If nothing else, it’s allowing the fish to breathe in the meantime and allowing some light into the lake,” Dubar says.

— Amanda Follett Hosgood