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Latest Northland invader? 'Bamboo'

Judy Gibbs, Duluth's invasive species eradication coordinator, is dwarfed by the large growth of the invasive Japenese knotweed, commonly referred to as "bamboo" growing along Chester Park Drive in Duluth on Monday, July 15, 2013. Bob King, Duluth News Tribune

DULUTH -- Another invasive species has reached the most-wanted list for eradication in Minnesota. This time it's Japanese knotweed - Polygonum cuspidatum - often referred to as "bamboo."

The plant actually is an Asian member of the buckwheat family, but it's tall (10 feet and higher), cane-like stems make it look and feel like real bamboo.

The knotweed recently has been found growing in backyards and wooded parks in Duluth and will be the subject of two hands-on workshops in coming days in Duluth where participants can find out what it looks like, how to get rid of it and help in the eradication effort.

The Minnesota Department of Natural Resources says Japanese knotweed is spreading from Maine to Minnesota and as far south as Louisiana. The DNR calls it a "significant threat," especially near water such as streams, lakes and wetlands, where it can survive high water and floods and spread before native species recover.

The invader tolerates full shade, high temperatures, high salinity and drought.

"I was out along Keene Creek (in Duluth), and it's just exploding out there up and down the banks," Judy Gibbs, the city's invasive species eradication coordinator, said. "The (June 2012) flood may have helped it along. ... I think we're about to get hammered by bamboo here in Duluth if we don't jump on this."

It's just the latest in a long line of aquatic and terrestrial invaders from afar that have begun to overwhelm native species, often because invaders aren't susceptible to local diseases and other afflictions. Some are changing the face of Minnesota's fields, forests and woodlots. Garlic mustard, spotted knapweed, purple loosestrife, buckthorn and others have been targeted for eradication, with varying degrees of success.

But eradication for this bamboo has proven to be tough. Fire doesn't seem to help. If you cut off one stem, another grows faster from the root system. Grubbing out the roots with tools can work but takes so much effort that it's impractical for large patches.

"About the only thing that works is chemical treatment, Roundup or Rodeo," Gibbs said. "This stuff grows so fast; people say you can watch it grow."

In fact, volunteers who help get rid of bamboo will be given bingo daubers filled with Roundup instead of ink.

"We'll cut them off between joints and then daub the Roundup on them. That should do the job," Gibbs said.

Japanese knotweed first was imported to the United States from Asia in the 1800s as ornamental shrubbery. It thrived because it was so hardy. Now it has escaped its original gardens and is spreading fast because of that same characteristic.

"It's not just plants it displaces, but insects that need those plants," Gibbs said. "Those kinds of (streamside) habitats are the only place you'll find a beautiful little damselfly called the Ebony Jewelwing. It would be a shame if we lose that little guy because of bamboo."

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