Phil MacKay of Parks Canada spreads tarps on knotweed in P.E. I. National Park. (Maggie Brown/CBC)

Parks Canada is trying to kill off an invasive species called Japanese knotweed that's been growing near the Interpretive Centre in the Greenwich adjunct to P.E.I. National Park.

It's part of a park-wide program to preserve native plants. Park ecologist Phil MacKay said this is the first year of a monitoring program to weed out invasive species.

For the knotweed, staff are focusing on 20 areas.

"We'll cut down the plant to ground level, and cover the area with heavy, black plastic tarps," he said. "The tarps will control the plant and kill it off basically."

Knotweed is hollow-stemmed and can grow two metres or taller in dense thickets that exclude other plants.

The hollow-stemmed knotweed can grow to more than two metres. (Maggie Brown/CBC)

"It'll come into an area, it'll take over, dominate an area, and eradicate the native species, therefore affecting your biodiversity and ecological integrity of an area," MacKay said.

Staff are also looking for four other species: garlic mustard, purple loosestrife, Scotch pine and glossy buckthorn.

Parks Canada doesn't know how the knotweed got into the park. MacKay says it was likely spread when dirt was moved around during construction of the interpretive centre.

He hopes the patches covered by tarps this year will die off and not sprout again in the spring.