Take on Invasives: Purple Loosestrife

This is the fourth in a monthly series on invasive plant species in Northern Michigan, their impact on natural landscapes and what can be done to help control and prevent their spread.

The pink and purple spikes sprouting from roadside ditches right now might look pretty, but behind their floral facade lurks the potential for millions of seeds that can ride the wind and spread this highly invasive plant across Northern Michigan.

Like other nonnative plants, purple loosestrife was introduced to the United States through ballast water of ships and commercial sale as ornamental shrubs. The perennial is a restricted species in Michigan — one that’s already established but prohibited from being sold — and poses a high risk of spreading and impacting native ecosystems.

Purple loosestrife growing along a riverbank.

In its preferred habitat of ditches, shorelines, riverbanks and shallow wetlands, purple loosestrife easily beats out native vegetation. Plants like joe-pye weed and cardinal flower, which support a number of native pollinator insects and hummingbirds, are quickly displaced by purple loosestrife infestations.

“It’s sad when those showy plants get outcompeted but its impact really goes beyond just a couple species,” said Rachel Leggett, Heartland Restoration Crew Lead for Huron Pines. “I’ve seen it where an entire marsh or riverbank is covered in purple loosestrife. With some infestations, it’s the only thing left growing.”

Huron Pines conducts its own treatments on public and private land across Northeast Michigan and partners with volunteer organizations to raise awareness of this invasive plant and remove it from the landscape. Among them is the Au Sable North Branch Area Foundation, a nonprofit group of landowners and river users who host an annual loosestrife pull near Lovells to keep the plant’s population in check. That effort, which has been going for more than a decade, is happening again Aug 16-17 in coordination with herbicide treatments by Huron Pines’ restoration crew.

“Our charter is to preserve and improve the watershed of the North Branch for the benefit of fish and wildlife,” said Bob Weed, the group’s treasurer. “We’ve been involved in an educational effort to make property owners along the river aware of purple loosestrife and have been undertaking an effort once a year to remove it by hand with the help of volunteers.”

A dense patch of purple loosestrife.

Pulling purple loosestrife in August keeps the plants from going to seed. It’s essential that treatments are done before seeds mature since each plant can produce hundreds of thousands — even millions — of tiny seeds which can be easily carried across the landscape by wind and water. Disturbing the plants after they have gone to seed only enables this spread. Hand-pulled plants and roots should be bagged and disposed of in a landfill. For plants that can’t easily be pulled whole, flower heads can be cut and bagged. This won’t kill the perennial but will at least keep it from going to seed for the season.

Those who wish to volunteer with the Au Sable North Branch Area Foundation’s loosestrife pull in August can email vice chairman Bill Anderson, waanderson49@gmail.com.

The Huron Heartland Invasive Species Network is made up of conservation groups, landowners, state and federal agencies that seek to restore native habitat through invasive species education, prevention and management. The Huron Heartland ISN is led by Huron Pines with support from the Michigan Invasive Species Grant Program (Michigan.gov/Invasives).

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