My elm tree leaves have green bumps on the bottom of the leaf. The bumps are...
My elm tree leaves have green bumps on the bottom of the leaf. The bumps are green, the diameter of a wooden match stick and appear in organized lines on the bottom of the leaf. They are perfectly round and protrude 1/8 inch from the leaves bottom surface. They are all uniform in size and are perfect little round green cylinders
Without a photograph to make a better identification; you likely have galls. Elms get leaf galls from a number of insects and mites.
Yours sound very much like nipple-gall psyllids. Now that galls are formed you aren't really able to do anything about it. They could also be eriophyid mite galls or galls caused by certain species of aphids.
Galling insects are rarely severely damaging to the tree. Only really extreme infestations that cause foliage loss wholesale are much to worry about, and, you would still have to plan to treat them in the spring before the galls begin to form.