The variety of invasive plants spreading in Point Pleasant Park in Halifax is on the rise, so a community council has asked for a new eradication plan.

The latest is the multiflora rose, a flowering plant native to eastern Asia and introduced to North America sometime in the late 1700s.

"The multiflora rose is considered aggressive but not noxious," said Brendan Elliott, a spokesman for Halifax Regional Municipality.

Aggressive means the plant spreads rapidly, but does not take over other species.

Eradication plan

Right now there are an estimated dozen or so of multiflora rose plants in Point Pleasant Park, but that could change dramatically in two to three years.

Councillors on the Halifax West Community Council have asked park officials to come up with a plan to remove the multiflora rose plants by this September.

"Our park staff will be meeting early next week," Elliott said.

"We're going to look at the entire species that we consider to be invasive in Point Pleasant Park and put together

a strategy."

Point Pleasant Park is struggling with invasive plant species such as Japanese knotweed. (Anjuli Patil/CBC News)

Extra stubborn knotwood

Park managers also consider Japanese knotweed, Himalayan balsam and Norway maple highly invasive.

Japanese knotweed has been particularly difficult to eradicate. Pilot projects using black tarps have had very little impact even if they were left on for five years, according to an information report published by city staff this week.

In that recent report, park officials said the practice was more effective on small, newly established patches

of knotweed but larger groves were too robust to be removed.

Success elsewhere

There has been some success in both Europe and North America injecting the bamboo-like stems of knotweed with a herbicide known as glyphosate, the report said.

HRM officials acknowledged trying that method of chemical eradication would mean getting a special permit.