I believe the thistle came from manure I used for fertilization in planting the red maple. It has now taken over the entire flower bed. There are also daylilies and hostas in the bed. This spring the thistle has spread into the surrounding grass as well. The thistle forms purple flowers at the top that die off like dandelions to spread. I've tried several popular store brands of weed killers that haven't worked, any ideas?
How Do You Kill Thistle?
Certified GKH Gardening Expert
You have either the bull or canada thistle. I can't quite tell from the photo, but I am leaning towards it being a canada thistle. You can identify for certain using the two following links:
Once you have determined which thistle it is, review the appropriate article below and recommended treatments: