Canada thistle - Ask Extension
I have Canada Thistle spreading quickly and don’t know how to get rid of it. It also is in the ditch along our road. Please give me information this...
Knowledgebase
Canada thistle #870984
Asked May 31, 2024, 3:44 PM EDT
I have Canada Thistle spreading quickly and don’t know how to get rid of it. It also is in the ditch along our road. Please give me information this is in Sodus Township
Berrien County Michigan
Expert Response
Where is it growing in addition to the ditch areas?
My house is on 5 acres.
it is in part of the lawn and we mow it. I have plantings And trees around much of the perimeter of our property and the thistle is very thick in many places.
Herbicides are often the fastest option to gain control over a Canada thistle population. There are some measures you can take to best protect the desirable nearby vegetation. The one I have used most recently is to cut the plants at the base and paint concentrated herbicide on the cut surface within a few minutes. In your case, concentrated glyphosate (e.g. Roundup Weed and Grass Killer Super Concentrate, though there are several other) is likely the best option. You can mix this herbicide as directed as well for a foliar application, however anytime you spray you risk off-target movement to your desirable plants, so I do not recommend that in an ornamental bed.
When using products containing glyphosate there are a few important points to consider. First, as with any pesticide, remember to read and follow all labeled instructions. Second, glyphosate is a broad-spectrum herbicide, meaning it will injure or kill other plants contacted during application, so care is needed to avoid green plant material, exposed roots, and injured bark of desired plants. Third, glyphosate is relatively safe in the environment when used as labeled. It adsorbs strongly to soil in most cases (i.e. clay and organic matter), allowing even sensitive crops to be planted shortly after application; meaning no carry over issues are expected. Fourth, glyphosate alone can take up to 14 days to show full activity under ideal growing conditions. Retreatment of the area may be needed depending on the degree of infestation. Glyphosate is most effective for perennial control in the fall but can be applied anytime the plants are actively growing (temperatures consistently above 50F). Finally, be sure that the product you choose has only the active ingredient glyphosate or glyphosate + pelargonic acid. Products with additional active ingredients may have other unwanted effects and may delay the planting of other plants in the coming season(s).
The best option to rid your lawn of this weed is the use of the herbicide triclopyr. This is the active ingredient in Bioadvanced Brush Killer Plus (recently renamed from Bayer Advanced Brush Killer Plus, you may see either). There may also be other products available, just be sure that the only active ingredient is triclopyr to avoid injuring your lawn. Applications made in the late summer to early fall (end of August through early October) are usually the most effective as perennials are moving carbohydrates to the root and rhizome system during that time and the herbicide will be more effectively translocated to that region then. Multiple applications may be necessary to rid your lawn of this perennial. As with any herbicide application, it is important to read and follow all labeled instructions.
When using products containing glyphosate there are a few important points to consider. First, as with any pesticide, remember to read and follow all labeled instructions. Second, glyphosate is a broad-spectrum herbicide, meaning it will injure or kill other plants contacted during application, so care is needed to avoid green plant material, exposed roots, and injured bark of desired plants. Third, glyphosate is relatively safe in the environment when used as labeled. It adsorbs strongly to soil in most cases (i.e. clay and organic matter), allowing even sensitive crops to be planted shortly after application; meaning no carry over issues are expected. Fourth, glyphosate alone can take up to 14 days to show full activity under ideal growing conditions. Retreatment of the area may be needed depending on the degree of infestation. Glyphosate is most effective for perennial control in the fall but can be applied anytime the plants are actively growing (temperatures consistently above 50F). Finally, be sure that the product you choose has only the active ingredient glyphosate or glyphosate + pelargonic acid. Products with additional active ingredients may have other unwanted effects and may delay the planting of other plants in the coming season(s).
The best option to rid your lawn of this weed is the use of the herbicide triclopyr. This is the active ingredient in Bioadvanced Brush Killer Plus (recently renamed from Bayer Advanced Brush Killer Plus, you may see either). There may also be other products available, just be sure that the only active ingredient is triclopyr to avoid injuring your lawn. Applications made in the late summer to early fall (end of August through early October) are usually the most effective as perennials are moving carbohydrates to the root and rhizome system during that time and the herbicide will be more effectively translocated to that region then. Multiple applications may be necessary to rid your lawn of this perennial. As with any herbicide application, it is important to read and follow all labeled instructions.
