September Elm

Rarely exceeding 20 m in height, the tree has a rounded crown with spreading to pendulous branches. The glabrous young shoots become progressively corky-winged with age, and bear oblong to obovate leaves <8 cm long. The wind-pollinated apetalous perfect flowers form pendulous racemes, which open in September and serve to distinguish the species from its cogenitor, the cedar elm U. crassifolia, with which it readily hybridizes. The samarae are oblong-elliptical, 10–15 mm in length, deeply divided at the apex, and ripen in November.

Before the outbreak of Dutch elm disease, U. serotina enjoyed limited popularity as a shade tree in the southern part of its range. The tree grows well on most soils, but is intolerant of anaerobic or saline conditions; it is also frost tolerant to -30°C (-23°F). The September elm is very rare in cultivation in Europe; it was briefly propagated and marketed in the UK by the Hillier and Sons nursery, Winchester, Hampshire, from 1972 to 1977, when 16 were sold. It is not known to have been introduced to Australasia. No cultivars of this taxon are known, nor is it known to be in commerce.