Removing mature Dandelions only works if you do it by hand. I have been managing my yard for 10 years and I have tried every weed killer imaginable with little luck. They're the Alpha weed.
Weed puller tool. I bought this at Home Depot. You can find it with the garden tools. It's awesome. I have a neighbor who uses a long screwdriver or a knife. I think this tool works better.
Isolate the root ball from the surrounding grass as much as possible.
Puncture the earth about 6 inches deep and 2-3 inches away from the plant base. If you are too close, you may sever the tap root which will regenerate the plant in a matter of weeks.
Push under the plant and force it to raise up. Carefully wiggle the plant around until it breaks free. This is not always easy, but with patience the little bugger will break free.
It's very satisfying to free your lawn of these. When you do it right, you'll get the whole plant. Don't leave any pieces of leaves or root because the plant can regenerate from those. Best of luck!
- 1.0 Stainless steel weed puller to