Home Pasture Health Forage Have You Discovered the Benefits of Canada Thistle?

Have You Discovered the Benefits of Canada Thistle?

Lewistown, MT heifer eats Canada thistle in pasture.
Bees on Canada/Creeping thistle by Richard Bartz courtesy of Wikipedia
Bees on Canada/Creeping thistle by Richard Bartz courtesy of Wikipedia

I have a different feeling about weeds than most people. That’s because I’ve turned them into forage. Read on for the benefits of one of my favorite forages – Canada thistle.

In 2004, I developed a simple method for teaching cows and other  livestock to eat weeds. It takes just eight hours spread over seven days and costs just $2.50 per animal. Once they’ve graduated, livestock students explore their pastures to add other weeds to their diet. They also remember year after year, and teach their herd mates what to eat as well. So it’s a one and done training.

I’ve trained cows, goats, sheep and bison, and over time, there was one weed/alternative forage, that became my favorite: Canada thistle (cirsium arvense, also known as Creeping thistle in Europe and in Australia as California thistle). Here’s what it has to offer as a forage:

• It’s the equivalent of alfalfa in nutritional value without the bloat issues.
• It is very resilient. It spreads via seeds and roots. It can grow in all kinds of climates, soils and precipitation levels, so it’s always there for us when we need some extra forage.
• Its flowers are pretty, they smell good, and they’re great for bees.
• It’s really easy to teach livestock to eat it. In fact, I think of Canada thistle as the “Gateway Weed.” Once cattle are eating it, they look at everything else in their pasture in a different way and begin to sample and graze a little of everything.

But Isn’t it a Pasture Menace?

True, not everyone appreciates Canada thistle they way I do. In fact, we’ve got a long history of hating it. Sir Anthony Fitzherbert, who published the very first farming manual in English in 1573, said that “thistyll was one of the weeds that greue mooste.” Carolus Linnaeus who developed the first weed classification system in 1753 considered it “the greatest pest of our fields.” In fact, people have disliked this plant for so long that before Canada existed, its name was “Cursed thistle.”

Lots of Canada thistle at Theodore Roosevelt National Park in North Dakota.
Lots of Canada thistle at Theodore Roosevelt National Park in North Dakota.

Cursed thistle immigrated to North America in the 1600s with the pilgrims. The list of laws requiring people to control it started with Vermont in 1795. By the 1800s it was so common in Canada that people assumed it was native, and that’s probably how it got the name we call it now. By 1865, the plant had become such a problem to farmers, that Canada enacted the first legislation for eradication of a weed:  The Canada Thistle Eradication Act of 1865.  By 1868 the state of Iowa wrote its own legislation declaring:  “…that if any resident owner of any land in this state after having been notified in writing of the presence of Canada thistles on his or her premises, shall permit them or any part of the root to blossom or mature, he or she shall be liable to a fine of five dollars and cost of collection for each offense.”

In spite of all our laws and efforts, Canada thistle persists. So maybe it’s time we look at it in a new way. So, here are some thoughts and answers to some questions I’m commonly asked.

Canada Thistle is Nutritious and Delicious and Can Improve Average Daily Gains

Lewistown, MT heifer eats Canada thistle in pasture.
Lewistown, MT heifer eats Canada thistle in pasture.

Since I started training livestock to eat it, I’ve known that Canada thistle is alfalfa-like in nutrition. That’s what makes it so easy to teach – it’s like candy to a ruminant. But the importance of this hit home at a conference I attended where a salesman was encouraging graziers to use his supplement tub.

“It’s 16% protein and will help your cattle gain 2.5 pounds a day!” he said.

“Wow!” I thought. “Canada thistle is that or better! Who knew that it could help stock put on so much weight?!”

Grazing Canada Thistle Means More Forage and Less Work

After a decade of teaching cows to eat weeds, I began to look at everything green in a pasture as forage. So where some folks thought they had grass and weeds, I did the math and realized that on average, they had about 43% more forage. Plus, once your livestock are eating this weed (and others) you’ll spend less time and money trying to control something that we’ve not had success controlling in 500 years.

Can Livestock Control Canada Thistle (or any weed)?


For resources on training livestock to eat weeds and what weeds are edible, check out the 2-ebook set and other articles and links here.

Eliminating a weed from a pasture is a hard thing to do, no matter the method you use. But I have had experience severely reducing a weed. For example, I managed the goat grazing in my pastures to maintain some beneficial Canada thistle, without letting it take over. I simply applied grazing pressure to it periodically. This same method worked on different varieties of knapweed and toadflax in pasture. In Boulder County, where I’d trained cattle to eat both, the rancher pointed out to me that while the weeds had decreased, the pasture grass he preferred had increased. I taught cattle in Marin County, California to eat Italian thistle. The rancher told me that he no longer had any Italian thistle on his property.

Are There Health Impacts Associated with Livestock Grazing Canada Thistle?

Canada thistle is a nitrate accumulator and if livestock have nothing else to eat, or if their rumens have not had the time to adjust to grazing them, the resulting nitrite poisoning can kill ruminants. This means that if we begin to look at these weeds as forage, we also need to understand how to work with our livestock to protect their health.

To ensure that your animals are safe:

• Never put animals on a solid stand of this plant. They must have other forage to mix with it to prevent poisoning.

• Give rumen microbes time to adjust to this plant. Introduce the food in small amounts over a period of 5 to 7 days.

• Don’t put hungry animals into a field that is largely made up of this weed. Make sure that they have a full stomach when moving to a new pasture with large stands of Canada thistle. This will ensure that they have the necessary carbohydrates in their rumen to aid the rumen microbes in breaking down nitrate.

Here’s How to Get Started Benefiting From Canada Thistle

All it takes is a few hours of your time and it’s actually a lot of fun. You’ll find all the resources and links to articles and videos you need right here:

Turn Your Livestock Into Weed Eaters



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Kathy Voth
I am the founder, editor and publisher of On Pasture, now retired. My career spanned 40 years of finding creative solutions to problems, and sharing ideas with people that encouraged them to work together and try new things. From figuring out how to teach livestock to eat weeds, to teaching range management to high schoolers, outdoor ed graduation camping trips with fifty 6th graders at a time, building firebreaks with a 130-goat herd, developing the signs and interpretation for the Storm King Fourteen Memorial trail, receiving the Conservation Service Award for my work building the 150-mile mountain bike trail from Grand Junction, Colorado to Moab, Utah...well, the list is long so I'll stop with, I've had a great time and I'm very grateful.