Problems with snow on the mountain and canadian thistle #239402 - Ask Extension


Problems with snow on the mountain and canadian thistle #239402

Asked April 24, 2015, 9:10 PM EDT

Any suggestions on getting rid of the invasive snow on the mountain, which is growing out of control, and Canadian thistle which has come back with a vengeance?

Baltimore City County Maryland

Expert Response

It would be helpful to identify the plants by their botanical name. It is confusing when using common names to identify plants as they can get used for more than one plant. Snow on the mountain is often referred to as Aegopodium podagraria ‘Variegatum’ bishops weed or you may be referring to Euphorbia marginata. This plant is in the spurge family and exudes a milky sap when cut.
Either way, the control is the same for either plant. Repeated efforts over several months will probably be necessary to destroy it. There are basically two ways for control. One method is to repeatedly dig up the plants and remove all the roots and rhizomes that are visible in the soil. Another option is to apply glyphosate (Roundup) to the area. Roundup may also have to be applied periodically over several months. Regardless of the method, persistence is the key.

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. Using a small paint brush to apply a non-selective herbicide to the cut ends of the top growth will further help to suppress/kill the plants. Follow label directions for timing of the herbicide. Please see the attached publication from the Plant Conservation Alliance for management options 

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