Taking on Japanese knotweed, a nasty invasive

By Dawn Tanner

Japanese knotweed is an invasive plant with a long history in the United Kingdom (UK) and other parts of the world as an extremely problematic species. In the UK, the presence of the plant on or even near a parcel of land negatively affects land values to the frustration and heartache of many property owners.

It’s not just a problem in the UK, it is a widespread problem in the northwest United States. And it’s also here in St. Anthony Park.

But there’s no reason to ­despair—not just yet. Japanese knotweed infestations in and near St. Anthony Park so far are small and fairly isolated. One infestation is located in Lauderdale just off Larpenteur Avenue West and Pleasant Street, not far from the Les Bolstad Golf Course. The other is located on North Eustis Street near West Bourne Avenue next to Highway 280.

To see these locations and get a better idea of the extent of Japanese knotweed infestations, visit the Early Detection and Distribution Mapping System (EDDMapS), developed by the University of Georgia. EDDMapS is a centralized reporting system for invasive species that includes distribution maps, site reports, photos, and treatment records. Do your best to become familiar with Japanese knotweed so you can report additional sites and help keep knotweed contained.

Identifying the knotweed

Japanese knotweed is distinctive and relatively easy to identify. One of its common names is Japanese bamboo because it produces hollow, upright, bamboo-like stems 3-16 feet tall. Stems, or canes, are often reddish or red speckled, and leaves are large with smooth edges. In areas where Japanese knotweed is present, thick single-species’ stands will be evident.

The Japanese knotweed infestation on Eustis Street is now a project that community members, the city of St. Paul, Ramsey County, and Minnesota Department of Transportation (MnDOT) are working together to control. Community members hand-pulled the full extent of Japanese knotweed and piled it onsite. Thank you to active neighbors, connecting with each other and working together!

The knotweed pile is being left to compost onsite to avoid any re-sprouting and accidental transfer that might occur by taking it to the County composting facility. Carole Gernes, Ramsey County Cooperative Weed Management Area (CWMA) coordinator, is pairing up with MnDOT to conduct the next treatment.

Japanese knotweed is especially difficult to control because no single method is effective for eradication. The plant re-­colonizes sites from underground rhizomes (roots that can sprout) and has been reported to travel via rhizomes for up to 65 feet. Hand-pulling, burning, smothering, or chemical treatment alone will not work, and successful treatment will only be accomplished by a multi-year effort with a combination of treatments. That’s why it is extremely important to maintain vigilance and work together.

The recent, first round of pulling that was completed in late May will set the plants back, deplete energy stored in the rhizomes, and produce a shorter stand by fall that will be more effectively treated with herbicide. When the knotweed are about 3-feet tall this fall, MnDOT plans to do the next treatment round. We’ll do our best to keep the community informed about progress. You can always check EDDMapS to see when treatment is conducted and get more information.

Once we get this invasive species under control, we can keep working on garlic mustard, buckthorn and others. Controlling invasive species takes a village. 

—Dawn Tanner is a resident of St. Anthony Park and program development coordinator for the Vadnais Lake Area Water Management Organization.

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