In an organic garden – weedkillers are never a viable solution. Weedkillers do immense harm to wildlife, people and planet. Fortunately, there are ways to get rid of thistles without resorting to these harmful chemicals.
How to Clear Lone Thistles
If you find just a few thistles popping up in a vegetable bed or elsewhere in your garden, the best way to deal with these is with simple hand digging and weeding. The key thing to note is that thistles regrow very easily from even the smallest section of root. Carefully dig down around a thistle (wearing gloves to avoid pricks) and ease the plants from the soil, trying to keep as much of the root system in tact as possible. (Do not add this to the compost, as it can re-root there). Continue this process as and when thistles regrow and it should be fairly easy to stay on top of the problem.
If the thistle is within a lawn or in cracks between paving, it may be impossible to remove the roots. Where this is the case, simply wait until the thistle has reached full growth (but flowers have not yet opened) and then cut the plant off at the base. Removing the green portion of the plant will starve the roots, and waiting until the plant has grown large before cutting it down will reduce the likelihood of regrowth.
How To Clear Large Patches of Thistles
If you are dealing with a large patch of thistles, this is a more prickly problem. However, there are still things that you can do to get rid of the problem, should you wish to clear the area in an organic garden or growing area.
If you have a large plot of land in a rural location, livestock grazing will get rid of thistles. Of course, this will not be a solution for most gardeners.
Gardeners may be able to clear large areas of thistles in summer by careful burning. Mowing mature plants (before they set seed) will also help, by starving roots. Mown areas can then be sheet mulched with organic matter, and a thickly planted cover crop sown to increase competition for resources and reduce the number of thistles that regrow.