Beating back the invaders:

🕔Mar 27, 2008

You may have seen him, shovel in hand, working along Highway 16 or up 37, his snow-white beard shining out beneath a farmer cap. Nearby will be his dark blue pick-up with “Graeme’s Agricultural Services” neatly painted on the door. This is Graeme Johnstone, a man who has spent more than 30 of his 80 years discouraging invasive plants.
When you see Graeme out there in the field, he may be accompanied by his working partner, his daughter Chris Johnstone. Using a sprayer sparingly, and a shovel and pick-axe liberally, they dig, pull and bag invasive plants.
Johnstone explains that we call plants invasive when they have been imported from somewhere else and—having few natural enemies in their new location—spread readily and establish quickly on new sites, choking out native vegetation. These invaders tend to have aggressive root systems and the ability to seed prolifically. They are often good hitchhikers, attaching themselves to livestock, wildlife, people, or vehicles—including construction equipment, logging machinery and trains.
Canada thistle is an example of an invasive plant with very effective seed dispersal. One plant sends thousands of fuzzy seeds into the late summer breezes. Johnstone, with his sharp weed-spotting eyes, has even caught a glimpse of thistle seeds at 3000 feet from the window of his plane (which he uses in Search and Rescue searches, as well as recreationally).
Invasive weeds threaten a wide variety of native plants. Native grasses and wildflowers cannot compete with tough invasive plants, and over time biodiversity is compromised, weakening the environmental health of an area. Meanwhile, alien weeds can reduce commercial crop production by as much as 40 percent, according to agricultural studies.
Plants to look out for
Johnstone and the Northwest Invasive Plant Council encourage residents to watch out for invasive plants. In particular, he targets spotted knapweed, marsh plume thistle, common tansy, and Canada thistle.
Spotted Knapweed (Centaurea maculosa) is a good example of just how tough invasive plants are. The Tseax lava beds, a mythical-looking rocky site north of Terrace,is home to determined lichens and—unfortunately—invasive plants such as spotted knapweed. The invasive seeds were likely carried to the lava beds by strong winds that blow up the Nass Valley.
This knapweed, up to 1.5 metres tall, has deeply cut hairy leaves and purple flowers. A black-tipped fringe on the bracts gives the plant its name. The plant reduces and can replace forage plants in a pasture. Sheep will eat the flowers and control the invader, but spotted knapweed is best pulled out, roots and all, before the flowers turn to seed.
Marsh plume thistle (Cirsium palustre) is described by Johnstone as a “horror show” of a plant, the worst offender in the northern part of British Columbia. Growing as high as two metres, its cluster of small purple flowers on a single spiny stem peek out above its neighbours. This weed does not occur in cultivated areas, but can invade moist fields and meadows where it replaces native vegetation and reduces forage for wildlife and livestock. It also forms dense stands that compete with tree seedlings planted for reforestation.
Johnstone recounts that his daughter Chris once spotted marsh plume thistle from a traveling VIA train. It was growing in a purple patch, many miles from any other infestations. He says he didn’t believe her at first, and flew over the site in his plane to see for himself. Chris was right—so she and Graeme hiked in to remove the plants, and still monitor the site twice a year.
Through their efforts, the Johnstones have managed to push the marsh plume thistle back to a controlled border, or “containment line,” outside of Prince Rupert.
Common tansy (Tanacetum vulgare) is a very hardy invasive plant that is potentially toxic to animals and humans. It grows up to 1.8 metres tall with dark green fern-like leaves and clusters of yellow button flowers. Johnstone classifies tansy as a “pickaxe plant,” indicating the tool one would use to uproot the beast. “It is up as far as Atlin, and the road up Meziadin,” says Johnstone. “It’s especially thick between Terrace and Prince Rupert.” Johnstone believes that a thorough digging and moderate chemical treatment is the best way to control this plant.
Canada thistle (Cirsium arvense) can be found along rail lines, roadsides and rangelands. On croplands it competes for light, moisture and nutrients. This plant thrives on disturbed sites, and Johnstone advises that fields should not be left plowed or tilled with no crop in, because an established crop can compete successfully with the thistle.

Working in the field
Graeme Johnstone, a Smithers resident, is one of a handful of contractors hired by the Northwest Invasive Plant Council (NWIPC), a non-profit organization based in Prince George whose mandate is to rehabilitate damaged ecosystems and to prevent further damage from alien plants. Graeme works the Skeena-Stikine and Houston areas, two of the seven Plant Management Areas coordinated by the NWIPC between the Queen Charlotte Islands on the west and in the Robson Valley to the east; from Quesnel in the south to the Yukon border in the north.
At NWIPC headquarters, Program Manager Andrea Eastham and her assistant Amy Barnes mind the phones and monitor the progress of the contractors in the field. Graeme and others are sent out to assess sites, record GPS locations of invasive plants, and fill out forms on location. Then they dig.
On the site, contractors dig out the individual plants—with as much root as possible. Roots, flowers, and seed-heads are sealed in plastic bags that will either be buried deep in a landfill or left on site to cook in the sun.
When herbicides are required they are, by policy, applied sparingly. Chemicals are applied early in the season when the least amount will be most effective.
Johnstone has less faith in chemical treatment than he did earlier in his career. At some sites, only manual (non-chemical) methods are used. But where there are particularly large or difficult infestations, a herbicide may be used first, followed by digging or pulling during subsequent visits.
All crews are expected to return to infested sites repeatedly to insure successful removal. Johnstone will return to the Tseax lava beds this spring, eager to see the results of last year’s fight. Weed contractors operate on a system of early detection, rapid response, and persistent site monitoring. As Graeme puts it: “You see a weed: you nail it, pull it, bag it—and then you look for it for the next ten years.”

Get involved
The NWIPC wants everyone to watch for invasive plants. If you think you may have spotted an invasive plant, Johnstone says, “bring it in to your local agricultural office, call me directly in Smithers (847 3453), or Wendy Siemens in Houston (845-7020), or call the NWIPC weed hotline at 1-866-44WEEDS (866-449-3337). We’ll take a look at it and see if there’s any action that should be taken.”
Graeme is very pleased with his efforts. “We’re winning on a lot of sites. There are some sites where the invasive plants have been entirely eliminated.” With the combined efforts of the public and weed contractors like Johnstone, we can help contain the spread of invasive plants and, in the case of some plants, prevent them from establishing in our northern ecosystems.
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