FAIRBANKS — Land managers in Alaska are experimenting with another weapon to use in their ongoing war against invasive weeds — black landscape fabric.
In an attempt to prevent the spread of perennial sowthistle on Chena Hot Springs Road, the Fairbanks Soil and Water Conservation District has covered three small patches of the yellow-flowering weed with black landscape fabric. All three patches are located along next to the road between 1 Mile and 3 Mile and comprise about 1,200 square feet.
The tarps, which are barely noticeable when driving by, were put down at the end of August using spikes to hold them in place. They will remain there for three years, invasive plants specialist Darcy Etcheverry with the Soil and Water Conservation District in Fairbanks said.
The goal is to prevent perennial sowthistle from spreading farther out the 56-mile road that leads to Chena Hot Springs Resort.
“There is no other perennial sowthistle farther out Chena Hot Springs Road,” she said. “We know using landscape fabric as a barrier will kill it if it’s left on for three years to deprive the root systems of nutrients.”
Perennial sowthistle is one of the Fairbanks Soil and Water Conservation District’s six invasive plants of concern. A native of west Asia and Europe, the gangly plant can grow taller than 4 feet and produces yellow flowers similar to dandelions. In Alaska, it is found mostly along roadsides.
“It’s considered a noxious plant in Alaska,” Etcheverry said. “It’s a very vigorous spreading plant because it sprouts from rhizomes (horizontal underground root systems).
“A lot of places you see it growing it’s one of the only plants growing because it just crowds out everything else,” she said. “We’re trying to prevent it from stretching out on every road leading out of Fairbanks.”
Perennial sowthistle is becoming more common along roadsides in the Interior — most notably the Dalton Highway — and Etcheverry acknowledges that without the use of herbicides there is probably no way to prevent it from spreading, but land managers may be able to slow the spread by using landscape fabric in specific areas like Chena Hot Springs Road.
Battling invasive weeds is a lot like fighting wildfires, Etcheverry said.
“You work from the outsides of infestations toward the center,” she said. “That’s the reason we put those tarps down, because perennial sowthistle is basically starting to move father out the road system.”
The highest densities of perennial sowthistle in town are in south Fairbanks, where tarping is not really an option, Etcheverry said. The infestations on Chena Hot Springs Road were small enough that tarping was feasible, she said.
It would be easier to use herbicides to kill the weeds, but doing so would require a permit, she said.
“To use herbicides on any Department of Transportation right of way we have to go through a permitting process and that’s very extensive and very expensive to do,” Etcheverry said.
The only other option is cut or pull the weeds several times each summer. It’s cheaper and easier to cover the patches of weeds with landscape fabric, she said.
“If we weren’t going to use weed barrier and weren’t able to use herbicides, we’d have to go out a couple times a month to cut it,” Etcheverry said. “It takes a lot of time and resources to do that.”
The landscaping fabric has only limited applications in the fight against invasive weeds, she added. The tarping project on Chena Hot Springs Road is an experiment to see how feasible using the fabric is and what other locations might be suitable for such an application, Etcheverry said.
“We’re never going to be able to tarp every invasive plant,” she said. “You might as well cover the entire state in concrete.
“We have to strategically manage the plants. That means choosing to manage certain invasive plants that have a higher chance of causing problems,” Etcheverry said. “We’re not out trying to eradicate chickweed. What we’re trying to do is target specific infestations we knew could have an impact on.”
The Soil and Water Conservation District has only one other spot it is using fabric on invasive weeds and that’s a patch of Reed canary grass on private property in south Fairbanks.
“When we tarped that last summer that was only known location of that plant in the Interior,” Etcheverry said.
Next week, the district is planning to use landscaping fabric in Chena Lake to cover two patches of elodea, an invasive aquatic plant that has been found in several local water bodies, including the Chena River and Badger Slough.
“We already have a clipping project out there,” Etcheverry said. “This is a way for us to collect information on how hard is it to install underwater and if it’s even feasible to do so.”
The district put up signs at each of the three tarped areas on Chena Hot Springs Road to inform curious passersby what was happening. The office has received a few calls from the public, which is all part of the project, Etcheverry said.
“Everything we do is about education,” she said. “If one person reads those signs and sees the picture and says, ‘I think I have that plant in my yard’ and calls us, then we’re making progress.”