If you can get Round-Up, or some kind of brush killer, cut off the top growth and put the herbicide full strength on the "trunk" top. If you can't get an herbicide, as some provinces at least can not, just keep mowing the growths down; eventually the roots left from the tree you removed will run out of juice to send up new root sprouts.

Tnx for the reply

brush killer with triclopyr in it is more effective than glyphosate which is in Roundup.

Do the cut-and-paint treatment as already described.

You need to determine if these are suckers growing from the trees roots or if they are seedlings from seeds the tree has dropped. Spraying suckers with a plant poison could kill the tree these come from and that is not a good idea. The most effective means of control of these suckers is to dig down to the tree roots and cut the suckers off there.

If these are growing from seed the easiest means of control is to cut the new growth off below any leaves so the new plants die.

kimmq is kimmsr

The tree's already been cut down. It's the suckers trying to keep it alive. I suggest mowing them when you mow your lawn or get a nice set of clippers. Eventually they'll stop popping up.