A tree 50 to occasionally well over 100 ft high; young shoots, leaf-stalks and flower-stalks conspicuously downy. Leaves 10 to 18 in. long, composed of usually seven, sometimes nine, leaflets which are oblong-lanceolate or ovate, rounded or broadly wedge-shaped at the base, slender-pointed, inconspicuously or not at all toothed, 3 to 9 in. long, 11⁄2 to 31⁄2 in. wide, nearly glabrous above but softly downy beneath, especially near the midrib and veins; stalk of lower leaflets up to 1⁄4 in. long; main-stalk round, not winged. Flowers produced during April on slender axillary panicles up to 5 in. long, the most noticeable feature of which are the cup-shaped calyces, 1⁄8 in. long and unusually large for an ash; petals absent. Fruits 21⁄2 in. long, 3⁄8 in. wide, often notched at the end.
Native of the E. United States from New York to Florida; introduced to Kew from the Arnold Arboretum in 1912. This fine tree is most closely akin to the red ash, but it has larger keys and leaflets, is more conspicuously downy, and the calyx, as noted above, is larger. The popular name of pumpkin ash is said to have been given to the tree because it is ‘swell-butted’, which means, presumably, that adult trees show pumpkin-shaped swellings near the base of the trunk.
The taxonomic status of this ash is uncertain. It is reported to be hexaploid (2n = 138) and is perhaps a true-breeding derivative from a cross between F. pennsylvanica (2n = 46) and a tetraploid form of F. americana (2n = 92). There are other possibilities, but there seems little doubt that the characteristics of the pumpkin ash are attributable to polyploidy, whether or not hybridity is also involved (Sylvics of Forest Trees of the United States, p. 188; G. N. Miller, op. cit., p. 21).