Alianthus altissima (Tree-of-Heaven) can produce suckers from the roots similar to aspen, and if the tree is a female, the suckers may instead be seedlings. A product such as a brush killer containing triclopyr or garlon is the best thing to use for ultimate control. You can spray this on the suckers, or apply it to the cut seedlings. If you are trying to kill a large tree, cutting frills in the bark with an axe or hatchet and applying some of the product in the cuts will also work. If you are careless with these products you will also kill any desirable plants in the immediate area. Be sure to apply these products carefully to the trees you want to kill. It make take several treatments.
A pesticide label is the law; read and follow all product recommendations.
