If you’ve spotted Canadian thistle creeping into your yard or garden, join the club. This weed spreads fast, digs in deep, and grows tall, making it one of the hardest to remove.
It’s not just a lawn care issue—it’s a constant battle. “The Canadian thistle is a notoriously stubborn weed to kill and its rough, prickly texture makes it a pain—literally—to pull by hand," explains Mary Jane Watson, Research & Development Senior Scientist at Spruce.
What Makes Canadian Thistle So Stubborn
Canadian thistle plants (also called creeping thistle) spread in two ways: its seeds float on the wind, and its horizontal roots crawl underground. You might find one or two plants one year. You may even think you killed them when you weeded, but many are surprised to find more and more every following year, until it's evident you're facing a weedy thistle infestation.
This happens because its root systems grow deep and wide. Pulling out the top might feel productive, but any piece left behind can regrow. And with sharp spines on every stem, managing thistle removal it is no treat either.
One Product That Actually Works Against It
Because it spreads both above and below the surface, these not-so-desirable plants need a two-front attack. Physical removal and surface damage only go so far; chemical treatments help slow it at the root.
"Spruce is a non-selective contact herbicide treatment that kills all types of weeds & grasses," highlights Watson. "Whether you’re looking to tackle thistle, dandelions, or crabgrass - Spruce works differently to break down their protective waxy coating and dehydrates the weed from the top down.”
That “waxy coating” is part of what makes thistle so resistant to many treatments. Spruce uses Sodium Laurel Sulfate to strip that layer away, which allows Cornmint oil to dry out the plant fast. Instead of needing to travel through the roots, it works on contact—starting at the surface where it matters most.
Spruce stands out because it works differently than traditional weed killers, and yes, it works better than white vinegar. The ingredients that promote dehydration cause the plant to collapse fast. Think hours, not weeks. With a thorough coating, the thistle can be defeated overnight.
When and How to Treat It
Target thistle when it’s actively growing—usually late spring through summer. This is when the difficult weed is pulling in water and nutrients, so it’s more likely to respond to treatment. A warm, dry day works best if you're applying Spruce.
Spray it directly on the leaves until they’re wet but not dripping. Avoid windy conditions so the effective herbicide application stays where you need it. Because Spruce is non-selective, don’t spray near grass or plants you want to keep.
FAQ
Can I just pull Canadian thistle by hand?
You can try, but it’s rarely enough. The extensive root fragments left behind when weeding go deep and snap off easily. And those spiny leaves? They make the job painful. Wear thick gardening gloves and dig deep if you go that route—but expect to follow up later.
Is Spruce safe to use around pets or kids?
Yes. Spruce doesn’t contain glyphosate that can be harmful. Once it’s dry, treated areas are safe to walk on. That said, always keep kids and pets off the lawn until it’s completely dry to the touch.
