A tree 18 to 20 ft high, with glabrous, square, slightly winged, slender young shoots. Leaves simple (rarely with two or three leaflets), ovate, sometimes roundish or obovate, tapered at the base, bluntish or pointed at the apex, inconspicuously toothed, 1 to 21⁄2 in. long, 3⁄4 to 13⁄4 in. wide, grey-green, glabrous on both surfaces; stalk 1⁄2 to 1 in. long. It flowers on the previous year’s growths, and the fruits are 2⁄3 in. long, obovate or oval.
Native of Colorado, Utah, and Nevada; said by Sargent to be not rare. Introduced in 1893 to Kew, where it formed a lax-branched, small tree, quite distinct from every other cultivated ash in the combination of square stems and simple leaves, but only worth growing as a curiosity. It is no longer in the Kew collection.