In the past several years Canadian thistle has proliferated over most areas of our property that haven't been cultivated. Elsewhere, we find numerous thistles randomly here and there. Fortunately, we have found that they are subject to the expected effects of the application of Glyphosate.

First we harvested as many of the seed heads as we could manage, but this was more of a burden for the two of us than we could manage before the seeds were blown away, across our property and onto neighbor's lawns as well.

One reliable way to stop the flowering of a thistle is to pull it up by the root.

The number of thistles requires back-breaking effort over days to pull up the annual stand, but I did give it a try once many of the thistles were beginning to flower. I wasn't sure that using Glyphosate would eliminate to threat of thousands of seeds flying in every direction.

Painting on Glyphosate is simply taking a small brush, dipping it into the solution and applying a coat to an individual plant.

In 2025 the spread was entirely across the southeastern corner of our property, approximately half an acre. One partly effective action is the pull each plant up by its roots before it blooms. That's back-breaking labor. Because we found last year that glyphosate does actually kill a growing plant, I began spraying a killing solution on this area. Because of the area and the number of plants just beginning to reach flowering, I considered tactics to cover the entire area as effectively as possible.

Where plants were less numerous, I began painting each with a brush containing the solution. But in most areas the plants were too numerous for this to be palatable. So I needed to operate more efficiently and hopefully more effectively.

I sighted on fence posts along the south and west sides, mapping the area between, for example, south fence posts 1 and 2 and west fence posts 1 through 6. I began spraying within each corridor as best I could, as I zig-zagged from one side of the corridor to the other. If I was standing within a corridor, I sprayed every thistle I could reach. I understood that I would miss a few, but hoped that the double coverage on each side would compensate.

The full cycle of the plants demise takes about two weeks. In a couple of days a thistle appears to be somewhat less green and a bit dried out. After about a week the leaves are beginning to curl and turning slightly brown. eventually a plant appears withered and brownish.

Given this extended cycle, I wondered how I would know if I had already sprayed within a corridor, my memory being less that exact. I was trying to cover as much of the half acre as I could be the plants bloomed and spread their seed loads.