Thistle and Garlic Mustard problem

Asked February 27, 2015, 12:49 PM EST

We are starting a permaculture farm and are having issues with, I believe, Russian and Canadian Thistle as well as garlic mustard. Is there a non-chemical way to get rid of these?

Branch County Michigan master gardener program permaculture invasive canadian thistle

1 Response

There are ways of controlling these plants but they are labor-intensive. The critical part of this is to get the problems out of the way before they bloom and produce seeds. If you wait, there will be many potential plants produced to be dealt with another year or years.

Cutting taproots...
Thistles have tap roots. If these are cut as deeply as you can get a tool into the soil, they should not return. There are tools that are narrow with a forked end that are pushed on an angle next to the plant and the taproot is severed. They are often used to remove dandelions, another taproot plant. It will not control weed seeds that may or may not have germinated.

Pulling...
Garlic mustard can be pulled as soon as it is seen in the late summer or early fall. It will produce seeds in the spring or early summer and they begin to grow the same season and overwinter as a rosette of leaves. But right now, in the spring, you will be looking for plants (rosettes) before they have bloomed. This plant produces seeds almost as soon as it begins blooming, so waiting for flowers is not the best method. You can eat the plant leaves by sir-frying them or dehydrating them and crumbling them over other dishes to give a mild garlic taste.

Smothering or solarizing...
If you have big expanses of a problem plant, you can smother them with layers of newspaper of cardboard. You could use clear plastic or black plastic with the edges weighed down so the plastic doesnot blow away (solarization). Paper can stay at the loacation but plastic would be moved to smother other weeds. For that matter, you could use old tar paper or boards. You are blocking the light. Clear plastic works better than black because it encourages weed seeds to sprout. But no method will kill off all seeds. That's the part of remaining ever-vigilant and knocking off the unwanted plants as little kids. You do not want to wait for flowers. You will aso have a number of years that seeds can germinate so that's the ever-vigilant part. It's actually more like decades of seeds lying dormant.

Homemade herbicides...
Products like vinegar do not usually kill weeds. They burn off the tops and they regrow from the roots. If you decide to try this, do a small area and evaluate it after a couple of months or a year. If your problems are returning, this might not be for you. As has been said: if it sounds too good to be true, it probably is.
Salt will ruin soil, so mixtures that include any form of salt will be counterproductive.