The invasive phragmites australis is forcing out the native type of phragmites as well as many other native plants in Michigan. The invasive variety are becoming widespread and threatening the health of Michigan’s wetlands and shorelines. They grow in dense stands as high as 20 feet tall and can deteriorate shorelines, block access for swimming and fishing, and create a fire hazard. The rate at which phragmites spread means early detection and control is imperative to saving an enormous and costly headache in the future.
Distinguishing the invasive variety of phragmites from the native can be tricky. The following table can help to identify the key differences.
We like to compare the mass of phragmites to that of an iceberg, i.e., most of its growth is below the surface. Although they appear massive above the surface, growing densely and more than 20 feet tall, the massive system of roots and rhizomes below the surface make up more than 80% of the plant. Rhizomes (horizontal underground stems) generate roots and stalks and can grow more than 6 feet per year. These rhizomes allow it to spread rapidly each year and even a single plant can multiply into a large, dense stand.
Control and Management
The best method of control for phragmites is herbicide treatment followed by mechanical treatment, prescribed fire, or water level management. Depending on site conditions and the type of herbicide utilized, treatment is usually most effective when done between early August and the first hard frost. Multiple herbicide treatments may be necessary. Post-herbicide cutting may also be necessary. This should be done at least 2 weeks after the herbicide treatment or after the first hard frost.