It’s a native of Japan and can’t be prevented. It’s not possible to throw it in the fire, submerge in it, or simply burrow it. Concrete is nothing more than lots of dust that it leaves.
It’s Japanese knotweed and it’s quietly dominating many roads throughout Southeast Alaska.
John Hudson, with the Southeast Alaska Watershed Coalition in Juneau spoke about the problems knotweed presents during the Alaska Invasive Species Partnership conference in Sitka in November.
“This plant has supernatural qualities supernatural qualities, which are not found in the ordinary,” he said.
Hudson is looking for ways to demolish the plant which is nearly indestructible.
“Apparently you can smother it in salt water and it shouldn’t suffer due to that,” he said. “You can chop the slicings and dump them in the sea for a few days, and they’ll get tossed away and then take root. If you’re determined enough to dig this up and dig the hole 15 feet deep in order to keep it inactive underground for 20 years.”
Hudson declares it to be the most destructive plant in Alaska and is often called the most destructive plant anywhere in the world.
“The creepy thing is growing through brick structures, constructions,” he said. “Look at the picture. This plant grew up an enormous brick structure that was thrown out of the top.”
The photo Hudson was used to show knotweed that grew through a structure was captioned “Relax! This is Britain.”
In Alaska the knotweed does not prefer the urban area however, it prefers the fringes of urban areas, particularly habitats where the popular salmonberry thrives, and where it is likely to eventually choke. There are around 400 knotweed-related infestations in Juneau as well as a little less in Sitka however, this is because Sitka’s roadways are smaller.
The problem isn’t entirely the plant’s fault. The reason knotweed likes highway pullouts and remote turn-arounds is due to the way people place it.
Hudson calls the event “Dump Your Stuff Sunday,” an American custom to drive across the street during the weekend and dispose of furniture, appliances and even yard debris. Hudson posted a second photo of of dead branches and leaves people threw away along on the roadway in Juneau. There among the brown stems, there were two bright green.
“Well If you take a close look at the pile of yard waste it is like a viable source of knotweed and it doesn’t seem to care that it’s the fall season or that winter is coming,” he said. “It’ll be able to withstand winter. Two years later, precisely. Here’s an adorable knotweed patch. It will increase in size the following year, and then double again every year after that, and keep growing. At the time it is needed it will be a hydro axe an mowing machine or snowplow is going to appear and will remove the knotweed — and that’s the source of all knotweed problems originate.”
It is not clear the origins of knotweed in Alaska. It’s a stunning plant, it’s likely was brought in as an ornamental, most likely being brought by a landscaper rather than a gold mining company or according to rumours that, by the famous naturalist John Muir.
When it did arrive, Hudson is committed to eliminating it. Hudson has discovered a recipe using 2percent Roundup Custom herbicide and 1 percent surfactant. When sprayed on the leaves late in the season of growth, will eliminate knotweed but only if you repeat the application every year for several years. He’s had the good fortune of obtaining the support from State Department of Transportation with this project, and soon could have a new colleague.
Oregon State University researcher Fritzi Grevstad visited Japan to discover knotweed’s primary adversaries.
“And that’s why this is an image taken in Japan and it’s very similar to the way that knotweed appears similar to this. It’s dirty and shabby,” Grevstad said. “And it’s because there’s an range of insects eating knotweed, as well as pathogens.”
Knotweed found in Japan is involved in a never-ending battle with a tiny insect – called a pisllid (Aphalar itadori) which has evolved to consume it exclusively. Grevstad was part of an international team that travelled across throughout Japan in 2007 to collect psyllids that eat all three kinds of knotweed and returned to test against a variety from native North American species related to knotweed. Following nine years of research the U.S. Fish & Wildlife Service issued an opinion that there was no substantial effect from the insect and Grevstad got a release license which gives humans a small allies in the fight against this pest.
“They’re extremely effective in destroying knotweed and removing it,” Grevstad said.
However, it’s not necessarily a guarantee that knotweed problems are solved. Grevstad has been working on biocontrol programs within the Pacific Northwest, releasing thousands of psyllids across eight states over the past three years. What did well in the greenhouse in conditions in the laboratory hasn’t been as effective on the ground, with a lot of psyllids unable to last after a few winters. The threat of predation from North American critters – like insects – could prevent the psyllids from making it through as well as other factors which may or might not exist in Alaska. Grevstad admits she doesn’t know what could happen if psyllids were allowed to be released into the Last Frontier.
“They might like this particular environment more,” she said.
Even if biocontrol does work, Hudson warned the members of the Alaska Invasive Species Partnership to never relax their guards against knotweed, or any other threat that may arise.
“Spoiler alert: everyone’s aware of that soil capsule from an Asteroid NASA has been currently sitting on, but they haven’t open it until now. Did you hear about the story?” Hudson said jokingly. “They extracted dirt from an asteroid located 100 millions miles distant. I’m aware of the contents.”
