A tree very similar in form and arrangement of leaf to the one-leaved form of common ash, but easily distinguished from it by the leaves being quite glabrous beneath, and narrower. Leaflets usually solitary, sometimes in twos or threes, in which case the terminal one is always much larger than the lateral ones, lanceolate, 2 to 5 in. long, 3⁄4 to 11⁄2 in. wide, tapered towards both ends, the margins set with coarse, sharp, outstanding teeth; dark lustrous green above, quite glabrous on both surfaces. Lateral leaflets, when present, 3⁄4 to 21⁄2 in. long, 1⁄4 to 3⁄4 in. wide. Stalk 1 to 21⁄2 in. long.
Some authorities consider that this ash is a ‘one-leaved’ form of F. angustifolia but the two examples at Kew have very dark brown, almost black buds and a bark very unlike that of F. angustifolia. They were received from Dieck’s nursery in 1889 and one measures 70 × 51⁄2 ft (1969). Although Henry discounted the theory that these trees are of hybrid origin, it seems to be quite likely. It is puzzling that another one-leaved ash at Kew, at present under the name F. e. ‘Veltheimii’, has a deeply ridged bark as in F. angustifolia (No. 80 in the Ash collection). This also came from Dieck in 1889, but as F. excelsior monophylla laciniata, a name usually given as a synonym of F. excelsior f. diversifolia. In Kensington Gardens, London, Alan Mitchell has measured three one-leaved ashes which have the strongly ridged bark of F. angustifolia and in this respect are in marked contrast to two examples of the one-leaved common ash growing nearby. These trees resemble the No. 80 from Dieck at Kew, but are probably older, the largest measuring 67 × 71⁄4 ft (1967).