How to Get Rid of Thistles Overtaking the Garden Beds

Got an email from Suzanne who says, ‘hi, what’s the best recommendation for killing the Canada thistle that has taken over our garden?’ And this will be answered by Matt.

I’m gonna use a more of a chemical control approach. So when I bought my house it was a bank repo, you know 20 some years ago, and nobody had done anything to it in quite some time, and there were thistles that were five feet tall and had trunks as big as my wrist. I cut all those off at about a foot above the ground and actually took Round Up and sprayed it down in the hollow tube of thistle. And so it went down in, got into the sap system of thistle; it did not kill 100% of the roots first application.

But what came back as it creeped up through the mulch? It was very low to the ground, very easy to spray and control. You have to be careful with Round Up that you don’t get over spray onto things you care about. It doesn’t work from the ground up. It works from the top down. So you don’t have to worry about it being on the soil near your plants as much as you need to worry about it spraying on the foliage of the plants. You don’t want to spray it on things that you want to keep.

And the same goes for the vinegar and salt, the organic method of that, that would work for the thistles, doing it the same way. But you do want to make sure that you’re not getting it on anything else. It doesn’t know the difference, so you just have to be very careful.

This would be a tough one to smother. Smothering does very well for a lot of things. A lot of times like when I’m starting a new bed or something like that, I’ll put wet newspaper down and then soil over top, and it kills the grass and that kind of stuff. This was a taproot, so it’s very down in there. It could kill off a lot of the little tiny ones, but even then it would be best to try to do something like an organic or a chemical application and preen in the future. That would help anything that would seed and stuff in the future, so it’ll just be a little just diligence.

So when I bought the house it took me that initial application, and then I would just walk the flowerbeds as they were starting to peek through, catch them when they’re really young, and I would spray that thistle. And it took me two seasons of spraying, but the first time you spray is the one that takes the longest. Because then your regrowth is much much less, but each time it draws more and more chemical down into that sap system in the root system, and the roots are really what we want to kill. It prevents it from ever coming back.

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