How to Get Rid of Thistle Plants in Your Yard

Expert Tips to Get Rid of Thistles

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Thistle is tricky because birds and butterflies love it, but gardeners and farmers hate it. We asked our gardening expert for advice on how to get rid of thistle plants.

“My vegetable garden has been overrun with thistles. I’ve spent more time and money trying to get rid of the thistles than I’ve spent tending to the vegetables. I’ve gardened in this spot for 25 years and never had a problem with it before. What can I do?” asks Birds & Blooms reader Joy Hattendorf of East Bethany, New York.

Gardening expert Melinda Myers says, “The hot, dry weather of the past few summers has increased the thistle population in many of our gardens. Our native thistles are less aggressive and a good source of food for pollinators and birds, but one nonnative thistle can produce thousands of seeds, allowing the population to quickly grow.”

Remove Thistle Plants Before Seeds Spread

Melinda explains you need to start managing this weed right away to get rid of it before it takes over.

“Timing is important when managing this weed. Digging is most effective when done before flowering occurs, but once the flowers emerge, cut back the flowering stem before the seeds form to prevent even more plants sprouting in next year’s garden.

If you opt for chemical control, focus on the first-year rosette of leaves. The plant is more susceptible to chemicals at this stage of growth, increasing your chance of success,” Melinda says. “Spot-treat them with a weedkiller labeled for this use. Burning, tilling and mowing early in May or June helps weaken and eventually kills existing thistles. Make sure the method you choose is safe for the rest of your plants.”

Psst—these are the worst invasive plants you should never grow.

Non-native Thistles Are Aggressive Weeds

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“We discovered Canada thistle growing in our yard. Should we get rid of it or is it good for wildlife?” asks Birds & Blooms reader Fran Armstrong of Spring Grove, Pennsylvania.

Melinda says, “Canada thistle (Cirsium arvense), like many thistles, is classified as a noxious weed in Pennsylvania and most other states. It’s very aggressive and displaces other native plants. These thistles can quickly infiltrate and take over the garden. Don’t let the common name fool you; this plant is not actually native to North America.”

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Bull thistle (Cirsium vulgare) is another aggressive, noxious weed to watch out for.

Discover more invasive flowers you may find in your yard.

Native Alternatives to Grow Instead of Thistle

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Add native plants with pollinator benefits to your garden instead. The Minnesota Department of Natural Resources recommends growing blue giant hyssop, purple prairie clover, Canada tick trefoil, rough blazing star, and wild bergamot for nectar-lovers.

Native Flodman’s thistle and wavyleaf thistle are better, more desirable alternatives for seed-eating birds like goldfinches.

Next, check out native ornamental grasses to grow for birds and butterflies.

About the Expert

Melinda Myers is the official gardening expert for Birds & Blooms. She is a TV/radio host, author and columnist who has written more than 20 gardening books. Melinda earned a master’s degree in horticulture from the University of Wisconsin-Madison.

Sources

• Minnesota DNR
• University of Minnesota Extension
• Penn State – Managing Canada Thistle