VIDEO and story: Knotweed invading city and residential land

Japanese knotweed, one of, if not the most aggressive invasive plants in the world, has arrived on the North Coast’s doorstep, video.

Alora Griffin presented a lecture on Japanese knotweed in April.



There’s a growing threat in Prince Rupert and it could be as close as on your very own property.

Japanese knotweed, one of, if not the most aggressive invasive plants in the world, has arrived on the North Coast’s doorstep and instead of knocking on the door, it’s barged in with a vengeance.

The exceedingly resilient plant has been spotted all over Prince Rupert – on federal lands, city property and in the yards of homeowners across town.

Lurking silently beneath the earth through a system of roots, Japanese knotweed (or fallopia japonica) can have roots that extend three metres into the ground and grow to be three to six metres tall.

The plant spreads through root and stem fragments dispersed through human activity, or they can be carried by water, according to the Northwest Invasive Plant Council, a B.C.-based organization.

The plant is characterized by its triangular-shaped leaves and long stems which resemble bamboo or rhubarb due to its round-hollow stalks. The knotweed thrives in moist to wet areas and can be found in gardens, near stream banks and coastal areas and in newly disturbed soil.

Not only a threat to Prince Rupert, the knotweed family, which also includes giant, bohemian and Himalayan knotweed, has been found all over the world, including in Britain, where the invasion has become so bad it’s a criminal offence to try and remove it yourself lest you spread it elsewhere.

A regional expert on knotweed

Prince Rupert resident Alora Griffin has done extensive research on the plant and recently gave a lecture on the topic through Transition Prince Rupert’s garden series.

“If you have knotweed in your garden, you cannot get a mortgage [in parts of the U.K.], you cannot get insurance and your neighbours can’t sell their property [in parts the U.K.] because it spreads that rapidly,” said Griffin in May. In B.C., insurance and mortgage issues have not arisen because of the plant.

“The plant is so strong, the chutes can grow through concrete, through metal and through asphalt. They can destroy septic fields. They have been known to grow through people’s foundations and tear down buildings because of it.”

The Northwest Invasive Plant Council (NWIPC) has identified eight species that have been found in Prince Rupert: Comfrey, English Holly, Common Tansy, Hawkweeds (orange and yellow), Himalayan Balsam, Marsh Plume Thistle, Oxeye Daisy, Scotch Broom and Knotweed (giant, Himalayan and Japanese).

But Public Enemy No.1 is Japanese Knotweed due to its destructive nature. Griffin wanted to learn more because with climate change, Prince Rupert may be in for more mild winters than normal, and hotter summers more conducive to invasive plants. May has also been declared Invasive Species Action Month in B.C.

Looks can be deceiving

It doesn’t help that the plant is aesthetically pleasing to the eye, said Griffin.

“It’s pretty. That’s why people keep it in their gardens and I’m a gardener. So what you do if you like a plant and you say to your friend or neighbour, ‘Would you like a piece of this plant?’ and I think that’s how it got over to Haida Gwaii – because people like it. It looks very pretty. It looks like a bamboo and bamboo can be invasive, but not as invasive as this,” Griffin said, adding Prince Rupert already deals with native species that can run amok like salmonberry, which also has an underground root system.

The treatment for these plants is extremely time-consuming and repetitive. Rather than try and dig up the roots or stems, Japanese knotweed needs to be treated with repeated injections of herbicide through by professionals directly into the stalks.

This needs to be performed multiple times over a course of two to three years before an area is completely free of the plant. Dead knotweed looks like brown, thin fallen branches and new knotweed can take its place just as easily in the same place if left untreated — even burning it is futile.

“This is something the community is going to have to tackle. The city has been in contact with the council because there are a few sites that have been identified … I think the key here is education. What is happening is people are dumping. They start digging it up out of their garden when it starts to take over and they dump it. But it can’t be killed,” Griffin said, adding that locations off Graham Avenue and on Mount Hays are identified to the council as dump sites (that shouldn’t be encouraged).

What the city is doing about the weed

City engineering coordinator Richard Pucci said that the education is vital for residents before the plant gets out of hand.

“The worst thing that could happen is if we get it at our landfill, because then it could just take over out there,” he said.

City communications manager Veronika Stewart added that there are a couple different ways that residents can contact the city if they find the plant.

“Japanese knotweed has been identified in several locations around Prince Rupert and our operations department is now looking at taking a proactive approach to managing it. We’re currently working with the NWIPC to develop a management plan for ourselves as well as the community at large,” said Stewart.

“In the meantime, if you spot Japanese knotweed in your neighbourhood or on city property, you can contact 250-624-6795 – that’s the public works department – to report it. Additionally, if you’ve got a smartphone, you can download the Report A Weed app for both Apple and Android phones to report the location of the plant and upload an image of it.”

“The herbicide has to be applied professionally,” said Griffin. “The plant councils work with municipalities and ministries and hydro, wherever the plant is identified. The councils hire the professional teams that come in and apply the herbicide.”

Additionally, city workers can remove the plant if properly trained they have been notified to keep an eye out for it while working outside. All public works employees have been trained on it, said Pucci.

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