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Winona County’s fight against Oriental bittersweet, a notorious woodland strangler

November 15, 2018 GMT

In Winona County, there’s an Asian vine that likes to strangle its victims to death.

It’s invasive. It’s aggressive. And there’s nothing bittersweet about it.

Besides the name, that is.

Winona County sustainability coordinator Anne Morse said the invasive vine called Oriental bittersweet has become a serious threat to Winona County woodlands. It kills healthy trees by wrapping itself around the trunk like a giant python heading to the canopy, then chokes the tree, and finally pulls it to the ground causing downed trees to pile up, making area trails impassable. The infestation seems to have started in Homer about 50 years ago and since then has spread through Winona, Wilson, Warren and Hillsdale. And it’s spreading aggressively.

According to Morse, the state has said Winona County has the worst invasion in Minnesota.

“The problem is that it grows exponentially,” Morse explained.

With how easy it is to spread — mainly because birds eat the little red and orange berries and then spread the seeds — it doubles itself in size every year. It also hasn’t helped that the vine and berries make beautiful fall and Christmas wreaths and have spread from people throwing old wreaths into their backyard, Morse said.

In 15 years, it can choke and kill a small tree, which is a short time in tree years.

And on top of that, the vine is hard to kill.

“The only way to get rid of this is you cut it down from the root, use herbicide and kill it,” said Liza Eng, a volunteer who has been helping Morse eradicate the plant.

If herbicide isn’t used, it just comes back, Liza said as she sat at a table with Morse and her husband Bruce — another volunteer.

“It’s after world domination,” Bruce said in a serious tone.

What does it look like?

Oriental bittersweet is not to be confused with another type of the plant called American bittersweet, which is a native plant that isn’t harmful to the environment here and doesn’t prefer to strangle trees to death.

The two are similar, but there’s one key difference to tell them apart.

The main distinction is that the native plant produces red and orange berries at the end of the vine, whereas the invasive plant produces berries all along the vine. The invasive version is also much more aggressive and can even grow the width of the vines to a point that they look like a small tree.

“It’s an American bittersweet on steroids,” Bruce said.

For those who have heard of another invasive species called buckthorn and are familiar with its invasion — Oriental bittersweet ranks beyond that.

“It’s way worse,” Morse said.

Gathering the troops

The good news is the county is fighting back.

Morse said the county is just ending its first year of hitting the battlefield with lots of chopping and eradicating.

But beyond ridding public space of the infestation, the most important piece of what they’re doing is spending hours with landowners teaching them what to look for and how to get rid of it. The county has even been providing the herbicide — which clocks in at about $150 per gallon — free of charge.