Flowering rush is an aquatic invasive plant that favors shallow water habitats and shorelines. The population in Forest Lake is the only known population in Minnesota that can spread by seed. Since the District began treatment in 2014, there has been a 99% reduction in population size.

Flowering Rush in Forest Lake

Flowering rush (Butomus umbellatus L.) is a perennial aquatic plant, native to Europe and Asia. It grows along lake and river shores as an emergent plant. Emergent plants are rooted in the lake bottom with stems and leaves that grow above the surface of the water. Forest Lake is the only lake within the District that is currently infested with Flowering Rush, and it is the only lake in the state with a population that can spread by seed. Most flowering rush populations can only spread through root fragmentation.

While it is often hard to obtain seasonal control of aquatic invasive species (AIS), an aggressive annual treatment of flowering rush in Forest Lake has resulted in a significant decrease in its population size. The annual treatment program of Forest Lake flowering rush began in 2014, at which point the population had infested almost 8 acres of the lake (340,740 square feet). With annual financial assistance from a variety of grants and partner agencies, the Comfort Lake-Forest Lake Watershed District (CLFLWD) has coordinated two or three herbicide treatments per year along with hand cutting of flowering seed heads.

The District typically conducts two surveys of flowering rush each year: one before treatment occurs and one after the treatment has occurred to determine the level of success. Native plants are surveyed alongside flowering rush and the District is careful to avoid areas of native plant growth during herbicide treatments. You can learn more about the herbicide treatments by reviewing the annual treatment notice.

Close-up of a blooming flowering rush plant

Topic Contact

Garrett Miller

Aquatic Invasive Species Coordinator

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