Two Non-Native Weeds Threaten Root River Through SE MN

AmeriCorps is playing a central role in controlling noxious weeds along the Root River in Fillmore and Houston Counties.

The Fillmore Soil & Water Conservation District is battling two non-native weeds that threaten the Root River in Japanese hops and poison hemlock, both of which are on Minnesota's Noxious Weeds List, choke out native species that shade streams and stabilize their banks - putting cold and clear water trout habitat at risk.

For the fourth consecutive season, a Conservation Corps Minnesota & Iowa crew located pockets of the weeds in Fillmore and Houston counties and treated them with herbicide. By mid-August, the two-to-three person crew had worked 456 of the 800 hours allotted and work is planned through late October.

As new infestations were discovered, the project's scope grew.

“The hops will continue to be an ongoing battle just because of the severity of the infestation along the Root River,” said Zach Dieterman from a Press Release from the Minnesota Board of Water and Soil Resources. The South District field coordinator for the Rochester-based CCMI crew in August 2018, Dieterman has since taken a job with the DNR. “The Root River is such a desirable and well-used recreational route for kayakers and tubers and people who are using the bike trail. It’s something that we want to keep as a nice natural resource for recreation purposes.”

When Japanese hops die off and go dormant, Dieterman said during the August 2018 tour of a treated site, they leave bare, erosion-prone riverbanks.

“We’re trying to get it back or maintain the kind of plant biodiversity that makes the Root River and the area unique,” Dieterman said.

Treatment in 2016 seemed to control the populations. Off-river and trailside work showed positive results, but high water in 2017 made riverside treatment too dangerous. After this spring’s high water and flooding likely moved weed seeds farther downriver.

In an Aug. 8 news release, the Minnesota Department of Agriculture solicited help from the public in reporting new finds and controlling Japanese hops. Infestations have been confirmed along the Root River from Preston to the confluence of the Mississippi River.

An MDA grant allowed Fillmore SWCD and Houston County Planning and Zoning to expand treatment this season, according to the MDA release.

The focus on poison hemlock, a biennial, centered on the Root River near Lanesboro.

Christina Basch, the Minnesota Department of Agriculture’s Rochester-based noxious weed eradication specialist, coordinates AmeriCorps crews’ work and surveys the sites.

“I am worried with these flooding events we’ll see more poison hemlock,” Basch said earlier this season.

As of mid-August, Basch said it appeared as if containment efforts were having an effect. Only a few new locations had been discovered. The MDA and DNR have seen a dent in poison hemlock populations where it has been treated.

During on-river treatment assessments of both weeds from Preston to Houston in mid-August, Basch said MDA and CCMI workers saw patchy but dense Japanese hops infestations. The effect of on-river treatments was noticeable, but large patches remained. Japanese hops didn’t appear in areas eroded by spring floods, but treatment was advised over the next few years. Treated poison hemlock sites showed no seed production. The crew observed two new poison hemlock sites.

Seeds of both invasive weeds are easily transported via animals, footwear or equipment. Partners have educated anglers and recreational trail users through posters and workshops.

“With hops, since it does create those dense mats, it can get almost like a snare where if people walk through it they can get trapped,” Basch said. Poison hemlock is highly toxic; ingesting a few leaves can kill an adult.

The SWCD, MDA and DNR are among those tackling invasive species in southeastern Minnesota before eradication becomes impossible or control becomes too expensive.