If you don't want to use herbicide, you can remove all the shoots you see every two weeks. Pull them off.

If you use herbicide, the safest and most effective way is to cut the shoot, then paint the herbicide on the cut surface,. (Get a product that's labeled to kill woody growth. Read the label; some can be used full strength this way.)

If you have a stump that can be recut, do so, then paint the herbicide on the outer two inches of the cut surface -- another words, in a complete circle on the cut surface.

No matter how you do it, this will be your new hobby for a considerable time -- at least two years.

The reason: you must starve out the roots.

Your other post
http://forums2.gardenweb.com/forums/load/trees/msg0619150218649.html

Here is a link that might be useful: your other post

When I had an aspen tree cut down, I found the most effective way to kill off the forest of suckers from the roots was to use a broadleaved lawn weed killer on them when they were about four inches tall. Two applications about a month apart did it once and for all. I realize that you may have a philosophical reason for not wanting to do this, but it's a very effective and practical way of ridding yourself of this nuisance once and for all. The stump and stub painting method suggested above works as well, but it can be a lot of effort to manually paint all of the stubs if you have dozens or hundreds, so you might want to consider a combination of both spraying and painting methods.

Thanks, everyone. I guess I'll just keep doing what I'm doing and hope for the best...and never let up.

I appreciate the input and your ideas.

I also have Poplars taking over my back yard. We just bought the house in Jan and knew it was a little grown over but didn't know to what extent. We picked up some stuff called "Stump out" which is in powder form. What you do is drill a hole in the stump and sprinkle the stuff in the hole. The label says it takes about 5 weeks for the stump to die. I will let you know how well it works if it does at all. Also I have been battling blackberry bushes all spring.

The best time to attempt killing trees in the fall when the trees are moving all the stored up nutrients from the shoots to the roots. Right now your herbicide applications are fairly useless because you will only kill the top growth and not the roots. Keep the trees in control until the fall and then try a systemic herbicide.

I hate to tell you this, as I'm generally in favor of milder and/or organic solutions, but I think your best bet here is glyphosphate (Roundup). Contrary to what weirdtrev says, it absolutely will kill the whole plant when applied to a stump or new growth (nor is there a mass migration of nutrients in the fall; there is one in the opposite direction in the spring, however). Just be careful not to get it on anything else, because it's a very effective plant killer (although it doesn't stick around, thankfully). Also, it won't work in the winter; the tree must be growing for glyphosphate to be effective.

In the future, if you want to kill a tree, consider girdling it and leaving it them up for a season before you cut it down.

just to add to indy78km, I remember my dad on a large tree would drill into the stump and put something in, don't know what, and a small/midsize tree he would spend weeks, digging round the base getting wider and wider, deeper and deeper, until he got to a point where the roots where thin, and cut the roots as best he could the whole time, and then invite a few of his beefiest friends over, with the promise of lots of beer! (after the task was over) and some would pull at the tree with ropes, and others would push, and my pop who was a tiny but strong man whould be at the tree cutting at any roots that had grown down from the tree (on the pushing side) and eventually there would be a cracking sound, men running and the whole tree, roots and all, would come crashing down!, but I warn you all this effort was for trees that where not more than about 25 foot! and pretty dangerious me thinks!
good luck with it, it must be totally frustrating.

I'm not sure if you're interested but I've been using Rock Salt, tossing it around has kept the small suckers away. When I had trouble with older sewer pipes getting clogged with Roots. The old timer that cleaned the drain suggested putting some down the drain. You can believe my Surprise when my Neighbors flowering Vines Began to die. I'm happy for plastic pipes and Rock Salt

you responding to thread that is 8 years old