canada thistle

Asked July 20, 2016, 11:34 AM EDT

I have previously used Roundup (sprayed onto the leaves, in sunshine ) and this has been effective, but I am concerned about the toxic side - effects of using Roundup. Can you suggest another preferable way of getting rid of this weed? Thanks!

Baltimore County Maryland

1 Response

With Canada Thistle the key to control is vigilance and persistence. Do not let the plant flower and go to seed. Mowing/clipping the tops whenever they appear will also help starve the roots. Other organic approaches include vinegar and soap sprays but are not effective as they burn the top growth only.
If you decide to use a glyphosate product as in Roundup, use a small paint brush to apply a non-selective herbicide to the cut ends of the top growth. Follow label directions for timing of the herbicide. Please see the attached publication from the Plant Conservation Alliance for management optionshttp://www.nps.gov/plants/alien/fact/ciar1.htm
Contact the National Pesticide Information Line for toxicity issues http://npic.orst.edu/
mh