Thistle #324236 - Ask Extension

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Thistle #324236

Asked May 23, 2016, 11:41 AM EDT

How can I remove thistle that has been allowed to spread and reseed a lawn area for a couple of years? I have tried pesticides, mulch, black plastic, etc., and the thistle seems to grow right through it. Thanks.

Anne Arundel County Maryland

Expert Response

Persistence is required, since seeds are almost certainly in the soil.
Thistle has an extensive root system so never rototill thistles. It is possible to hand dig seedlings in soft soil, if all root is removed. Do not allow flowering or remove flowers before seed forms. In lawns repeated mowing can exhaust the root system. You can also clip the weed at the base. 
More than one application is necessary to get rid of thistle. Paint glyphosate, active ingredient in Roundup and others to foliage or fresh cut stems when actively growing in the spring and fall. 
See publication on thistle http://www.nps.gov/plants/alien/fact/ciar1.htm

mh
Some additional comments from a gardener in MD:  You state using pesticides, but they never kill weeds.  Also you state it is a lawn problem, but that is not consistent with using mulch or black plastic.  Glyphosate can be sprayed in gardens (if does not contact desirable plants) but not lawns. In lawns, painting is recommended as HGIC responded.  Always read labels to ensure the product is for your problem. Thistle is a tough weed that is not killed by most herbicides, but you can prevail.
good luck
GEO L Replied May 23, 2016, 7:34 PM EDT

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