Thistle Patrol

Although Creeping Thistle can be beautiful while in bloom, its aggressive nature isn’t so beautiful.

What’s tall, prickly, and extremely persistent? Canada thistle, but Diana Baragar — founder of the Thistle Patrol — would prefer we call it by its other common name: creeping thistle. “Calling the plant Canada thistle gives the impression the plant is from Canada, but it was introduced here from Europe,” says Diana. Once the plant arrived from Europe it began to spread and colonize, out-competing native plants for space and resources. The weed is now widespread across Canada and locally it is prevalent in Edmonton’s natural areas.

It is quite possible that Diana holds the world record for most creeping thistles pulled by human hands; a record that comes from 15 summers of pulling the invasive weed. She organized the first Thistle Patrol pull in 1998 in response to pesticides being sprayed in Mill Creek. Diana recognized that along with the creeping thistle, the native plants growing in the area were also being killed by the pesticides, and she committed to pulling the weed to stop the spraying.

The founder of the Thistle Patrol, Diana Baragar pulling thistles in Mill Creek.

The founder of the Thistle Patrol, Diana Baragar, pulling thistles in Mill Creek.

When I asked Diana if she could estimate how many creeping thistle she has pulled over the years, she was hesitant to give an answer. “I have no idea,” she said. “If I knew the answer to that question I would probably be taken aback.” Considering we had worked together for an hour pulling creeping thistle and in that time managed to amass three huge piles of the weed, I assume the number would be staggering. The number of thistles Diana has pulled continues to grow with her commitment to running the Thistle Patrol weekly during the summer months.

Ed Retzer cuts down Creeping Thistle with his scythe in Mill Creek.

After one hour of pulling we had cleared most of a small bank on the southeastern edge of Mill Creek ravine. I could see the difference our work had made in this small area, but in the grand scheme of things I wondered if we were really making any longstanding impact. It was then that I met Ed Retzer — a man in his 80’s wearing a green flat cap and carrying a scythe — who had been working away from me on the upper part of the bank. He has been Diana’s most committed helper over the last ten years. He reminisced of his days as a child visiting Mill Creek when the area around the ravine had been farmland, and it was obvious the area holds meaning for him.

Ed continued to tell stories of his childhood, and around 30 minutes later he was on the topic of the uses of hydrogen peroxide. While I enjoyed listening to his stories, what I was really looking for was the reason he had dedicated ten years of his time to pulling thistles. I used a small lull in his story to interject my question of why he had dedicated so much time to this cause. “I wouldn’t be doing this every week if I thought it was a waste of time.” Ed said. “For every weed we pull we prevent hundreds of more seeds from getting into the soil, and next year the thistles won’t be as bad.”

The long taproot of Creeping Thistle gives it the upper edge over native plants growing in the area.

Ed is right — an ounce of prevention is worth a pound of cure. Although we had only cleared one small bank of the creeping thistle, we had prevented thousands of seeds from being dispersed in the soil, and we had reduced the need to spray herbicides in the area.  We had made a much bigger impact than just a small section on the southeastern corner of Mill Creek. Our conversation finished with discussing need to get more people involved in helping to control invasive weeds. “If everyone took one hour a week to pull some weeds in our natural areas, think of the difference we could make,” Ed said.

“Weeding for Wildflowers” is the slogan on the small signs Diana sticks into the ground near the area the Thistle Patrol is working. Since creeping thistle is a such a competitive plant it can easily overtake our natural areas like Mill Creek, reducing the biodiversity of other plants present. This in turn reduces the biodiversity of other organisms as they can no longer use the area the thistle has encroached on for nesting or feeding. Perhaps the most rewarding part of the evening was clearing the creeping thistle away from some native Canada anemone trying to grow in the area that was in danger of being choked out. Knowing this native plant can now continue to grow made the hour spent pulling more than worthwhile.

Canada Anemone, a much more desirable plant to have growing in Mill Creek, is rescued from the onslaught of Creeping Thistle.

Canada Anemone, a much more desirable plant to have growing in Mill Creek, is rescued from the onslaught of Creeping Thistle.

If you would like to help with the Thistle Patrol weed pull in Mill Creek, Diana, Ed, the native plants, and all the organisms we share Mill Creek with would be grateful. The pull takes place every Tuesday night for one hour at differing locations in the ravine. It’s great exercise, great conversation, and a chance to enjoy the beauty of Mill Creek while working to protect it. To be placed on the contact list or for more information please email Or, if you are interested in organizing your own weed pull in one of Edmonton’s natural areas you can visit the Partners in Parks page on the City of Edmonton website.

Before and after photo of the small bank Diana and I cleared of thistle, preventing the release of thousands of seeds.

Myself and Master Naturalist Colleen Raymond are all smiles at the satisfaction of pulling invasive Creeping Thistle.

Photos: Jason Teare

If you enjoyed reading this post you may also enjoy the post Garlic Mustard Weed Pull.

Mow ’em down. Pull ’em up. Move ’em out.

A new noxious weeds awareness campaign has been launched by the City of Edmonton. The city has distributed posters and flyers, and is running a radio ad to raise awareness of a few of our most common invasive weeds. The goal is to motivate citizens to remove these weeds from their property to prevent further spread of invasive plants into our natural areas. Once these plants spread into our natural area parks and river valley, they can choke out native plants and form monocultures that reduce biodiversity. It is this biodiversity that many organisms depend on for survival in our city.

Here are the 6 weeds the city has targeted in the noxious weeds awareness campaign:

Canada ThistlePlant: Canada Thistle (Cirsium arvense). Although it’s called Canada thistle, this plant is not native to Canada; it has been introduced from Europe. The plant has prickly leaves with clusters of flowers that range in colour from purple to white. The plant can grow up to 1.5 meters tall.

Wanted For: Being an aggressive, colony forming perennial that can use its creeping roots to spread up to 4.5 meters. Dense infestations impact wildlife by reducing food sources and nesting areas.

Control: Tilling the infested area is not effective as it produces small root pieces that can develop into new plants. Repeated mowing or hand pulling will deplete the root system over time, but must be done regularly for a period of years. Do not let the plant go to seed before removing, as this will aid in its spread.

perennial sow thistlePlant: Perennial Sow Thistle (Sonchus arvensis). Introduced from Western Asia. Plant grows up to 1.5 meters tall and produces yellow, dandelion-like flowers and seed heads with soft, white bristles.

Wanted For: Its deep root system and ability to spread extensively by both seed and creeping roots. Chemicals from decaying plants can inhibit the seed germination of native plants.

Control: Newly germinated seedlings are easily controlled by pulling, which is best done before a deep root system develops. Mature plants can be mowed or pulled, but must be done regularly for a long period of time to exhaust the root system. Tilling is not the best form of control as small roots pieces can spread and germinate.

Scentless ChamomilePlant: Scentless Chamomile (Tripleurospermum perforatum). Introduced from Europe. Produces white daisy-like flowers with a yellow centre. Finely divided carrot-like leaves that produce no scent when crushed. Plant can grow up to 1 meter tall. This plant can be confused with shasta daises — a common ornamental plant sold at greenhouses.

Wanted For: Its high seed production. Mature plants have been reported to produce 300,000 to 1,000,000 seeds which can remain active in the soil for many years.

Control: Mowing will prevent seed production, but digging up the plant with as much of the root system as possible is required for permanent eradication.  Tenacity will be required for well-established plants.

Leafy SpurgePlant: Leafy Spurge (Euphorbia esula). Introduced from Europe and Asia. Has long, narrow leaves and greenish-yellow flowers that grow in umbrella-shaped clusters. Grows up to 1 meter tall.

Wanted For: Its extensive, persistent creeping root system which can extend 4.5 meters wide and up to 9 meters deep. A mature plant can produce up to 100,000 seeds which are ejected from the seed pods up to a distance of 5 meters! Plant contains milky latex that can irritate skin.

Control: It is important that removal of this plant begins as soon as it has been identified in your yard. Mowing will prevent seed production but it is best to hand pull young infestations. Wear long-sleeves and gloves to prevent skin irritation. It may take years of pulling to completely eradicate the plant.

Creeping Bellflower

Plant: Dame’s Rocket (Hesperis matronalis). Introduced from Europe. This plant looks very similar to garden phlox, and as such it can be difficult to convince a homeowner to remove it. Garden phlox has 5 petals while dame’s rocket has flowers with 4 petals that bloom in lavender, pink, and white. Plant can grow up to 1 meter tall.

Wanted For: Its high seed production. It quickly forms dense infestations in Edmonton’s woodland areas.

Control: Refrain from planting wild seed mixes as they can often be contaminated with Dame’s Rocket and other invasive weeds. Best controlled by hand pulling or digging as roots come out easily. May require more than one year of pulling to control if seeds have been allowed to enter the soil.

creeping bellflower

Plant: Creeping Bellfower (Campanula rapunculoides). While in the same family as our native harebell, this plant is not native and has been introduced from Europe. It produces bell-shaped, nodding flowers that range in colour from purple to blue. Plant can grow up to 1 meter tall.

Wanted For: Its beautiful flowers which deceive homeowners into allowing it to grow in their yards. This plant has aggressive creeping roots that can travel under lawns and concrete sidewalks. It also spreads by seed.

Control: Tilling is not effective as it spreads small root fragments which will sprout new plants. Mowing will control seed production but extensive digging of the area to remove creeping roots will be required. It can take many years of digging to eradicate this plant.

There you have it – our city’s top 6 noxious weeds that are best removed from your property. By controlling these plants, you will help prevent them from spreading further into Edmonton’s natural areas where they can be even more difficult to control than in your yard. Edmonton’s wildlife and native plants will thank you for it!

Let’s get weeding Edmonton!

If you enjoyed this blog post you may also enjoy: The War on Invasive Plants
Photos: Jason Teare