Overholt first noticed phragmites near White Lake in 2017. "I discovered to my surprise and a bit of horror that we had this plant on our doorstep," he said. Now, with the help of environmental groups and lake associations, he's been ramping up efforts to manage its spread. Dave Overholt has been working with Lanark County, environmental groups and lake associations to manage the spread of the invasive phragmites in Lanark County.(Submitted by Dave Overholt) Expensive plant to control Invasive Species Act in 2016, and is one of the most expensive plants in Ontario to control, according to Jolanta Kowalski, a spokesperson with Ontario's Ministry of Natural Resources and Forestry.