Groups combating the spread of knotweed

Coalition offers free removal

Uncontrolled Knotweed can overtake roadsides and interfere with visibility, as shown in a photo taken in Norway.

KINGSFORD – Hailing from Japan, where its roots cut through volcanic rock like butter, Japanese knotweed — and a few other species including giant and Bohemian — can thrive in the Upper Peninsula and northern Wisconsin.

The plant invades a wide variety of habitats unimpeded.

Knotweed looks just like bamboo and is often referred to as such because of its hollow, segmented stems. The leaves are typically large and heart-shaped and are alternately set on “zig-zag” stems.

Later in the growing season, knotweed will develop clusters of small creamy or greenish flowers. It can honestly be quite showy and attractive, but don’t let this aggressive invader fool you.

This plant can grow up to 20 feet tall with an extensive, and destructive, root system. The plant has rhizomes capable of spreading up to 65 feet away from the main patch to send up new shoots.

A close-up of knotweed’s bamboo-like stem.

Remember how in its native range knotweed grows on the sides of volcanoes? There its rhizomes are known to break through hardened lava. Here, this can spell trouble for urban areas where knotweed is known to damage building foundations and asphalt roadways.

Since knotweed is tolerant of a wide variety of habitat conditions it rarely stays put. Knotweed is a master at spreading, using stems and root fragments to grow new plants vegetatively.

That means when a broken stem floats downstream, or a section of root tissue breaks off — even as little as a half-inch — those plant parts can set down roots and start growing new plants.

The plant also promotes soil erosion when it dies back in the fall. While growing along lakes and streams it can be particularly damaging to riparian areas.

Luckily in recent years state and local officials have recognized the threat posed by knotweed. Both Wisconsin and Michigan have regulated invasive knotweed species to legally restrict the plants being bought, sold, planted and transported.

To combat the spread and prevent damage from this invader, the Wild Rivers Invasive Species Coalition has secured grant funding to work on controlling and managing knotweed throughout a five-county management region.

The Wild Rivers Invasive Species Coalition is a local cooperative invasive species management area whose goal is to promote invasive species management through education, outreach, monitoring and control.

WRISC manages invasive species throughout Dickinson and Menominee counties in Michigan, and Forest, Florence, and Marinette counties in Wisconsin.

Currently, WRISC is able to offer treatment of priority knotweed infestations free of charge to landowners in an attempt to stop this invasive species in its tracks.

Think you may have knotweed on your property? Contact WRISC Coordinator Lindsay Peterson at 906-774-1550 ext.102 or wildriverscwma@gmail.com.

To learn more about WRISC and local invasive species management efforts, go to www.wrisc.org.


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