Ulmus crassifolia

Cultivation Details

Ulmus crassifolia grows mainly in the Gulf Coastal Plain of N. America, which has relatively mild temperatures throughout the year. The average mid winter temperature in the region is around 8°c, in summer it is around 28°c. The average number of days without a killing frost is 236. The mean annual rainfall can vary from 460 - 1,470mm^[1]. Prefers a sunny position but can succeed in light shade. It thrives in deep rich soils, where it becomes a large tree, but also tolerates dense, poorly drained clay soils and can be found on dry limestone hills, though it is small and scrubby in this environment^[1]. A fast-growing tree^[1]. The tree is relatively shallow rooted in early life and is resistant to root pruning in the nursery. In later life the trees are moderately tolerant of soil compaction or disturbance of the root systems^[1]. This species is susceptible to 'Dutch elm disease'^[2], a disease that has destroyed the greater part of all the native elm trees growing in countries such as Britain and USA. The disease is spread by means of beetles. Mature trees killed back by the disease will often regrow from suckers, but these too will succumb when they get larger. There is no effective cure (1992) for the problem, but most E. Asian, though not Himalayan, species are resistant (though not immune) to the disease so the potential exists to use these resistant species to develop new resistant hybrids with the native species^[3]. The plant hybridizes with Ulmus serotina^[4]. When grown together in cultivation, open pollinated hybrids between the Chinese elm (Ulmus parvifolia) and this species have been recorded^[1].