The major differences between the cultivar and species are a less vigorous growth rate resulting in a smaller mature tree, and smoother bark. The claret ash normally achieves a height of 25-30 feet, but may reach 50 feet or more in some cases. Young trees are rather narrow, but eventually become more broad, developing into a handsome rounded tree. The leaves are pinnately compound, with 7 to 9 leaflets. The margins are sharply serrated or saw-like.
Leaves occur in somewhat of a whorl along the branches.
Leaflets are typically 2 to 3 inches in length and the entire leaf is between 6 to 10 inches overall. The lacy foliage is a dark lustrous green through the summer months. In the fall the leaves turn a brilliant purplish-red, resembling the dry claret wine of the Bordeaux district of France. This is the calling card for which this tree is prized. By most accounts, this cultivar is seedless.