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Invasive Japanese knotweed is popping up all along the Mad River watershed and in local farmers’ fields, thanks to Irene flooding as well as the reconstruction efforts that followed.

 

While the immediate effects of Irene on local farms were devastating in terms of land lost and crops contaminated, the long-term residual effects present an equally devastating set of circumstances.

The invasive and noxious Japanese knotweed is thriving on local fields and spreading throughout the Mad River watershed. Knotweed is commonly found in the riparian buffer, along riverbanks and along some roadsides in The Valley. Its root system is robust and is able to throw down roots in virtually any environment.

After the Mad River flooded, leaving many plants displaced and earth disrupted, knotweed spread beyond the riverbanks and into the agricultural land, in many cases.

NEILL FARM

Elwin Neill of the Neill Farm in Waitsfield said the invasive species has sprouted where the floodwaters flowed through his fields. Neill said he has “quite a crop of it through the alfalfa” and said getting rid of it is a challenge.

“It’s going to spread; there isn’t much we can do it about,” he continued.

SANTA DAVIDA FARM

David Hartshorn of the Santa Davida Farm in Waitsfield said he predicted the knotweed outbreak in August.

“I knew it was going to happen; there’s not much up here, but down at American Flatbread it’s in all the fields,” he said.

“It’s a big incubator along the river and all the dirt they are moving is going to be an incubator for it now; that’s just the way it is. Some of it is shallow and barely on the surface and laying down roots. Some of it is in long sticks. I pulled a stick out that was five feet long and an inch down in the dirt,” Hartshorn continued.

Hartshorn said farmers can till to keep up with the knotweed, but “nobody’s going to till in the peripherals, and it encroaches anywhere that isn’t managed. It’s here and it’s a much bigger problem now.”

Hartshorn took a sample knotweed plant to the Flood Relief Headquarters in Waitsfield to educate people as to its appearance.

FRIENDS OF THE MAD RIVER

Caitrin Noel, director of the river advocacy group Friends of the Mad River, said that the knotweed was spread by flooding as well as by the equipment being used to restore riverbanks and farm fields. The plant is a rhizome which spreads via its root system and can survive in the gravel that is moved from site to site post flooding as well.

“We started seeing knotweed along the roadsides where recovered dirt and gravel were used to repair roads after the 1998 flood,” she said.

“It’s too early to tell the extent of its spread from this flood. I’m encouraging people to reach out to flood headquarters or Friends of the Mad River for volunteer support if they see a lot of knotweed on their land. This could be an opportunity to remove it now before it gets established,” she said.

At the Sugarbush snowmaking pond on Route 100 behind Mac’s in Warren there was knotweed before Irene and there is knotweed evident as the pond is being restored and the riverbanks returned to their previous course.

“We have not seen an increase in the amount of knotweed,” said spokesperson Candice White.

 In restoring the pond, Sugarbush has excavated some 45,000 cubic yards of topsoil, plus an estimated 10,000 cubic yards of gravel. The resort is having the dirt tested and, if it is not contaminated from the flooding, is offering that dirt to local farmers and others interested.

White said that as of this week, the enormous pile of dirt and gravel are not showing signs of knotweed growing through them.

SMALL STEP FARM

Jillian Abraham, owner of Small Step Farm along the Mad River in Waitsfield, noticed knotweed sprouting throughout her entire farm in the weeks after the flood. During the flood, water reached eight feet deep on the property, ripped out three acres of vegetables and destroyed infrastructure including the washing station and greenhouses.

“The knotweed is sprouting and emerging across the entire property; endless roots and shoots are scattered over and beneath the bulldozed silt and topsoil. There is a one-acre section, just south of the hoophouse, where it is a much denser stand. It is emerging in different stages, some are just sprouting through, some is over a foot high,” Abraham said.

“This plant, with its damn network of rhizomes, could completely take over this property in the spring. So, it's time to do something about it now. I am told by the National Resource Conservation Service and a number of Vermont farmers that it certainly came in with the flood water. It probably also came in with the fill, but that can't be proven at this time. And, I'm not going to be the one to point that finger without definite evidence,” she said.

Abraham said she has three options for dealing with the invasive plant: hand pull, cultivate with tractor or spray with an herbicide. She is not keen on spraying, even with an aquatic-friendly spray, and to use a tractor means not disking or rototilling.

“You cannot disk or rototill, if the plant gets chopped you multiply the problem. So, a tine weeder or spring tooth harrow with c-shanks could possibly be used to bring the pieces (as small as half inch will sprout) up and out of the soil,” she explained.

So it’s hand pulling for her.

“Hand pull—yes, we are. This Friday afternoon and Saturday morning we are hosting a knotweed scavenger hunt. The trick is that you can't just yank it up, you must fully get the wood (root/shoot) that it is sprouting from. Then, it must be put into a garbage bag or burned. We will have to hand weed more than once, because it is not all sprouting at once,” she said.

“When asking other Vermont farmers, which I've received about 20 responses, it ranges from ‘Just walk away...and spray for a future healthy field" to ‘just cultivate, fallow the field and do whatever you would do normally in the spring.... Just make sure you have a cultivating tractor to use weekly,’” Abraham added.

Caitrin Noel reported that the Nature Conservancy suggests cutting knotweed four times a year for five years which will weaken the plant to the point where it will die.

KINGSBURY FARM

To her south is the Kingsbury Farm where farmer Aaron Locker reports that there is some knotweed in the fields but said that it is not his biggest concern right now as it is growing in a garden setting and is shallow rooted.

“While it is relatively persistent I don't expect it to go to seed in our fields. It poses a greater threat on the riverbanks as in that setting it chokes out trees and other vegetation whose roots are not shallow rooting and have the potential to stabilize the riverbank,” he said.

For Locker, the bigger concern is not the knotweed that came in with the flood but the soil that left. His farm lost three-quarters of an acre, about 10 percent of the tillable land.

“The lost land was the buffer but it moves with the river. We would not till any closer, even without the buffer. Of equal concern is the loss of topsoil on another acre. This includes several sections in our movable greenhouse field. Those sections will remain out of production until soil tests indicate that we have built them up to a level that makes it possible to support a vegetable crop,” he said.

SIMPLICITY FARM

To the north, Simplicity Farm owner and farmer Doug Turner said thousands of knotweed plants have sprouted across his fields on Route 100 in Waitsfield. He and his son have worked to clear off three fields and have posted a request for volunteers to assist with knotweed before the corn is cut.

“It’s the most prolific plant I’ve ever seen. “I’m not sure using a brush hog would do any good. If you don’t pull them and get all the roots, they’ll pop up in the spring,” Turner said.

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