This is the sixth and final installment of 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.
A receding Lake Huron is contributing to a resurgence of one of Michigan’s most notorious invasive plant species.
Phragmites, a reed grass capable of reaching 15 feet in height, can’t grow in water more than a few feet deep. When Lake Huron rose to record highs in 2020, it flooded shallow sandbars and drowned phragmites that had been growing there. Now that levels are falling again, those dormant roots are coming back to life and sending up their towering shoots once more.
“We’re seeing some of those old populations coming back, especially along the shore near Tawas,” said Logan Hawley, Coastal Restoration Team Lead for Huron Pines. “Once it establishes itself, nothing else grows.”
Introduced to the United States from Europe, phragmites has been a persistent and destructive invasive in Michigan for decades. It is commonly found growing in ditches, wetland areas and along lakeshores. Phragmites can spread incredibly quickly with the aid of tendril-like stems, called rhizomes, that snake 20 feet across the ground and send up vertical shoots along their entire length. Its seeds are carried long distances by wind and waves, and broken stem fragments can re-root, further hastening its spread.
The problem with phragmites lies in the sheer density of its stands combined with its immense height. Phragmites infestations block waterfront views, prevent native plants from growing and obstruct the movement of waterfowl and turtles. Large offshore patches can disrupt wind and wave action needed to replenish beaches and dunes with sand.
Invasive phragmites is easily identified this time of year by its fluffy, hand-sized seed heads atop tan shoots. These structures remain standing through winter and resemble tall field corn. Michigan also has a native phragmites. Though not very common, the native species is shorter, less dense and has reddish stems.
Targeted treatment with herbicide, either by hand or spray application, has proven to be the best way to control phragmites.
“We see high, high effectiveness with our herbicide treatments, especially on mature stands late in the year,” Hawley said.
It’s also vitally important to clean, drain and dry watercraft between uses, since phragmites seeds can easily stow away in bilges, live wells and anywhere else water collects in a boat or kayak.
Phragmites infestations can be reported through the Midwest Invasive Species Identification Network at misin.msu.edu, an online database Huron Pines uses to prioritize future treatment work.
The Huron Coastal 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 Coastal ISN is led by Huron Pines with support from the Michigan Invasive Species Grant Program (Michigan.gov/Invasives).