There are two main kinds of thistles that get into lawns. One is the Scotch thistle and one is the Canada thistle. One is easy to remove and eradicate; the other is very difficult. Both can be a pain to the barefoot in the grass folks. They both have sharp thorns. The pain of walking on them is not pleasant but it is worse if the thorn breaks off and ends up as a sliver in one’s skin. How do you get rid of them?
The Scotch thistle is the easy one. Although if left to flourish it can reach a height of 3 feet, it normally will tolerate being mowed. Its purple flowers are large and interesting. It is dark green in colour and has a wider leaf than the Canada thistle. It grows as a single plant and one could dig it up and remove it. It also is easy to control with the usual lawn weed killers.
The Canada thistle is the toughie. It has a lighter green foliage that is narrow. It can also reach heights of 3 feet and also has purple flowers. Both thistles have seeds like dandelions that can blow in the wind. In the summer, I have been driving along some city roads when the air is full of the seeds blowing in the wind, much like dandelions parachuting their way into new territory. I know they are thistles because the seed heads can be seen along the roadsides where the weeds have not been cut.
Canada thistle spread by underground rhizomes. Rhizomes are underground stems. If you see one Canada thistle, it is likely attached by a rhizome to another plant a little distance away. If you are planning to dig out the Canada thistle, make sure to dig out the rhizome. If you don’t it will regrow, and you will still have thistles. Canada thistle does not respond well to herbicides. The plants will be killed off, but often the rhizomes continue to live and soon they will send up new sprouts from underground. Only continuous attacking of the Canada thistle will suffice to eradicate this pest from your lawn or garden.