I don't know about products to kill roots, but definitely apply some type of brush killer when you cut it down. Products like Brush-b-Gon and Roundup's Woody/Poison Ivy/Brush killer. Those are available at Lowes/Home Depot. Other products like Garlon are available at farm supply stores like Tractor Supply.

Be sure to put the herbicide on the thin green layer just under the bark layer - you don't have to slather the whole stump with it, just the perimeter. Mimosa does usually try to sprout from the roots. Just keep nipping the sprouts off when you see them; don't let them get any bigger than you have to (otherwise they are feeding the roots as they grow - you want to starve this plant to death).

The herbicide will be taken down into the roots by the living tissue layer (the cambium), but some sprouts may persist anyway. Persistence is the key.

Would girdling and then applying the brush killer work any better. It seems like cutting it down would limit any 'living activity' to bring the brush killer down to the roots.

Thank you esh ga.
Dottie, that is a very good point. I need the brush killer to travel and work. Thanks for bringing that up.
Still thinking on this.

Carla

According to this site:

Girdling is effective on large trees where the use of herbicides is impractical. Using a hatchet, make a cut through the bark encircling the base of the tree, approximately six inches above the ground. Be sure that the cut goes well below the bark. This method will kill the top of the tree but resprouts are common and may require a follow-up treatment with a foliar herbicide.

Making any cut in the bark (either by girdling or cutting it down) will allow you to apply the brush killer to the living cambium layer. That layer will transport the herbicide to the roots. There doesn't have to be anything above it.

Here is a link that might be useful: source

Girdling is not merely a cut, but the actual removal of a few inches of the bark through the cambium layer all around the tree to suspend the nutrients from feeding the above ground tree portions. This, especially at this time of year would likely signal the roots to sprout a new trunk in place of the damaged one.
Perhaps a 3/4 girdling or simply drilling holes all around the trunk and several applications of brush killer would be more effective.

How big a mimosa tree is this? A chainsaw, drill for a few deep holes, and Roundup did the trick for the 10-20' ailanthus scattered around my property. Some had calipers of 12" or so. They suckered, and I sprayed that growth as well; then they died. But if the mimosa is much bigger, girdling might be a better option.

I think I have a plan. Cut it down, drill holes and use brush killer in the holes. It will probably be a timely process but I have to get rid of this mimosa, which really has very lovely blossoms. Feel free to discuss my idea.
Thank you for your knowledge and help.

Carla

If the holes are in the middle of the wood, don't bother with putting brush killer in them. The brush killer needs only to make contact with the green layer of tissue (the cambium) that lives just under the bark (kind of like when you scratch the bark and you see green?). All the wood in the center of the trunk is essentially dead, it will not send the chemicals down to the roots.

Here is a link that might be useful: Tree anatomy

I hope someone discussing the Mimosa might help me with some opinions and answers on getting rid of buckthorn. The snow has finally melted here in New England and I'd like to experiment with doing bark treatments on buckthorn. I have a couple of questions

I'm hoping my costs down for this experiment period. I understand Garlon 4 is the right herbicide for this. I haven't found another formula of Triclopyr ester labeled for this use other than Garlon 4, is there one? Maybe something cheaper? If not, is there a place where one might purchase a smaller quantity than 2.5 gallons at 300 plus dollars?

I'd like to not use diesel so I don't piss off some of my neighbors. Where does one get mineral oil in sprayable quantities? All I've found so far is pints for laxative use :-) Is bark oil available in smallish quantities anywhere and is it worth using instead of mineral oil or diesel?

I'm eagerly looking forward to trying a different technique other than the Weed Wrench attack on the buckthorn. Thanks very much for your assistance, and be assured this information will get quietly spread around the Boston area.

Note: I did look into earlier year's postings but found no answers there.

jpal, you might ask your questions on the Trees forum.

token, thanks. I will get some of that stuff.
Thanks everyone, I feel pretty confident that I can kill it now. I do love the blooms though. :-(

Carla

my mimosa tree has died over the winter months. there are new sprouts coming up around the trunk. why did it die?

Mimosa is listed under "Severe threat" on the NC exotic invasives list. Good to get rid of it.

I had a beautiful Mimosa tree, was approx. 7 yrs. All the leaves started falling off and it died. could it have been a blight?

Yvonne7261, Mimosas are subject to a soil borne fungal disease that kills them, especially in the South.