Combatting the alarming Japanese knotweed/Janet Marr

“Picture your favorite trout stream or canoeing river lined for miles with a tangle of rigid, bamboo-like stems 10 feet tall, making access to the river impossible and threatening healthy fish habitat.”

This alarming quote comes from a Wisconsin brochure describing the non-native Japanese knotweed (Fallopia japonica) that has invaded rivers from Washington State to the East Coast. Japanese knotweed’s underground stems (rhizomes) are known to push their way under streets and up through pavement (as in Bayfield, Wis.,), parking lots, sidewalks and foundations, resulting in huge repair costs. After escaping from yards and gardens, Japanese knotweed can quickly become an invasive pest in natural areas forming dense stands that limit other plants from growing among their crowded stems.

Unfortunately, Japanese knotweed and its invasive cousin giant knotweed (Fallopia sachalinensis) are alive and well in the Copper Country. One or both of these perennial species occur in the Houghton/Hancock area, on U.S. 41 between Houghton and Chassell, Calumet/Laurium, L’Anse, Lake Linden and nearby towns, and elsewhere in the Keweenaw. The good news is that spread of these two out-of-place knotweed species that are native to Asia can be slowed and new introductions can be prevented in the Keweenaw.

Come learn more at a KISMA-sponsored knotweed talk and control demonstration on Sept. 24, 2013, from 1 to 3 at Houghton’s Lakeshore Center’s (old UPPCO Bldg) Community Room. Pam Roberts (Northwoods Cooperative Weed Management Area coordinator) will talk about Bayfield’s struggles and successes with Japanese knotweed control. Ian Shackleford (Ottawa National Forest botanist and invasive species specialist) will demonstrate various control methods.

What is KISMA? Keweenaw Invasive Species Management Area’s mission is to facilitate cooperation and education among federal, state, tribal and local groups and landowners in prevention and management of invasive species across land ownership boundaries within Baraga, Houghton and Keweenaw Counties. KISMA is funded by a Great Lakes Restoration Initiative grant provided by the U.S. Environmental Protection Agency through an agreement between the Houghton Keweenaw Conservation District and the U.S. Department of Agriculture, Forest Service, Ottawa National Forest.

Both Japanese and giant knotweed have deep taproots and extensive networks of rhizomes that may extend horizontally up to 65 feet. They are big plants up to 10 feet or more in height and have large broad leaves and hollow stems with swollen nodes resembling bamboo stems. Their small white/creamy flowers appear in August and September in spikes near stem ends.

NOTE: Japanese knotweed is a Michigan Prohibited species, meaning that the plant or plant fragments should not be sold, purchased or intentionally moved through plant exchanges. Control should be in a manner that prevents spread and further infestations. Cutting and moving plant parts to other areas will only make the problem worse. Seeds and fragments of stems and roots can produce new plants, so care should be taken to double-bag them for disposal. Please contact KISMA for proper disposal info.

If you see a Japanese/giant knotweed patch or would like more info, please contact me(Keweenaw Invasive Species Management Area or KISMA) at 906-337-5529; jkmarr@mtu. edu or Sue (Houghton Keweenaw Conservation District) at 906-369-3400; sue_haralson@yahoo. com.

Here’s a good website to find out more: JapaneseKnotweedBCP.pdf.