Click below to listen to my Garden Bite radio show: Combating Canada thistle
No, it’s not really from Canada! It’s other “handles” are ‘Lettuce from Hell thistle’ and ‘Cursed thistle’. I don’t really get the ” lettuce” part, but I concur on the “from hell” part.
If you try to till this beast under, you’ll only multiply it! Plants can start from broken off roots. Digging it out is okay if there’s not much but will take a couple of seasons. Do NOT compost roots or seed parts – unless your home compost pile gets to 150 degrees.
You CAN compost the foliage but let it dry in the sun for a few days on a paved surface – burn that baby! That is the other option, burning it. Check your local ordinances before you do that!!!!
The best organic method is to keep mowing it down until the plant weakens and then plant a cover crop like hairy vetch, crimson clover or rye. You can then compost those cover crops! This will take a couple of seasons.