The leaves and buds of Ulmus thomasii are very similar to those of U. americana. There are usually some branches of Ulmus thomasii with pronounced corky ridges, but there are none on U. americana. The growth form of Ulmus thomasii is a strong central trunk with recurved lower branches. U. americana usually branches low into a broadly spreading canopy with the lower branches rising strongly.

Ulmus thomasii is distributed throughout the state, but is far less common than U. americana. The greatest concentration of records of U. thomasii are mid-northern from about Taylor County east to Marinette County. It is probably more common than the records show, because it can be difficult to distinguish from U.americana. The commonest associated species in northeastern Wisconsin, in my experience, is Prunus serotina.