Knotweed problem thorny

  • Jun. 11, 2010 11:00 a.m.

Soaking with salt has worked in some knotweed infested areas, but chemicals might be the only solution for getting rid of a ticking time bomb in Queen Charlotte, said Keith Alexander contractor for the Northwest Invasive Plant Council. Knotweed is an invasive plant found at several sites in the village, including Spirit Square and Phase 2 of the Community Park (beside the Skateboard Park). It was once sold as an ornamental species and is extremely difficult to kill, Mr. Alexander explained at the June 7 QC Council meeting. “It is a patient time bomb just waiting for a human to move it somewhere,” he said. The plant spreads through its roots, which delve up to 10 feet into the earth, and can grow again from a tiny shard, so digging it up is not a feasible solution. “You also have to be extremely careful if moving it, that its not dropping out the back of the truck,” he said. Mr. Alexander said his predecessor, Mike Cheney, developed a method of spraying knotweed leaves with salt water, which had limited success. Last year, he took that a step further and soaked the roots of the plants with 7,500 gallons of salt water an hour. A patch of Himilayan knotweed on Husband Road has responded well to this treatment and now seems dead (it didn’t come back after last year’s spraying). Salmon berries, thimbleberries and other plants are coming back though. The problem is that Japanese knotweed which is found at the Spirit Square and Community Park site does not respond as well to this treatment. It also takes a year to wait and see if the plant comes back. “To my mind there is only one solution, glyphosate,” he told council, but, as a contractor, he is not allowed to use chemicals on the islands. Mr. Alexander said that First Nations communities in Washington State were also opposed to herbicides in the past, but they have a huge issue with knotweed colonizing their salmon streams. Not only do the plants choke out indigenous species, but they provide poor stability control. So when a patch invades a stream bank, eventually the bank slides into the river due to erosion. Thus the knotweed travels to another location and salmon spawning habitat is compromised. Places in Europe are spending millions of dollars to get knotweed under control, he said. In some construction projects, the ground is dug five feet down and a layer of very expensive landfill cover material is laid down before a foundation can be poured. Banks in England will not allow mortgages on land that is occupied by knotweed. The plant is so strong it can grow through cement and stonework. Mr. Alexander said the islands still have relatively small patches and it’s not in the salmon streams. To keep it that way, he hopes to use chemicals in a limited way. “We have a choice, turn a blind eye or nip it in the bud,” he said. In Washington State, they developed a method of injecting herbicide into the stem of each plant, which kills the root. “It was either that or lose their streams,” he said. Mr. Alexander thinks that if Queen Charlotte wants to develop these areas, they need to do something quickly. He said the patch near the Skateboard Park is the biggest one he knows of. Saltwater is still a good method, said Mr. Alexander, not only is it cheap, but there is an inexhaustible supply. But sites that are not near the beach are trickier to reach. At one site, he had to enlist the help of a small dog (bribed by a milk bone) to feed a hose through 90 feet of culvert. If he had a water tank, he could reach more areas and asked whether council would be able to help. He also noted that he has only a small budget for the entire islands and would appreciate any work the village can do themselves. Mayor Kulesha said the fire department would be a good place to ask, as they used to use salt water for fire fighting and may have something. Mr. Cheney also tried mulching areas by covering them old carpet and other materials, but Mr. Alexander said these efforts have had limited success as well. Mr. Alexander also warned that some gravel pits on the islands are infested with knotweed and use of these is allowing the weed to move around. Mayor Carol Kulesha said the knotweed at the Community Park site was brought in a load of dirt.