Common Name:

General Information

Ulmus crassifolia is a deciduous tree with a rounded to narrow crown; it can grow 6 - 27 metres tall. The bole of mature trees can be up around 90cm in diameter[, ].
This is one of the four species that are harvested commercially for their wood, known collectively as 'rock elm'. The other three species are Ulmus thomasii (which is the actual rock elm), Ulmus alata and Ulmus serotina. The tree is grown as an ornamental shade tree in southern N. America[].

Known Hazards

The tree flowers about the same time as the ragweeds (Ambrosia species) in southern N. America and its pollen is known to cause or to complicate later summer hayfever[].

Botanical References

Range

Southern N. America - northern Mexico, Texas, Oklahoma, Arkansas, southwestern Tennessee, western Mississippi and Louisiana

Habitat

Stream banks, low woods, low hillsides, roadsides, waste places; at elevations up to 500 metres[]. Usually found on moist, limestone soils along water courses with other bottomland trees, but also grows on dry limestone hills[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Deciduous Tree
Height	20.00 m
Growth Rate	Fast
Pollinators	Wind
Cultivation Status	Ornamental, Wild

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[].
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[].
A fast-growing tree[].
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[].
This species is susceptible to 'Dutch elm disease'[], 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[].
The plant hybridizes with Ulmus serotina[].
When grown together in cultivation, open pollinated hybrids between the Chinese elm (Ulmus parvifolia) and this species have been recorded[].

Edible Uses

Leaves - raw or cooked. We have no specific information for this species, but the very young leaves of all Ulmus species can be eaten, and generally have a mild flavour[].

Medicinal

Collectively, the bark of all species in the genus Ulmus may have anti-inflammatory effects in the gut[].

Other Uses

The tree is tollerant of atmospheric pollution, often being grown in cities. The leaves can be used as indicators of the severity of air pollution. The sulphate content of leaf samples shows the long-term exposure to sulphur dioxide, which is related to overall pollution levels[].

The wood is known for its great strength and exceptionally good shock resistance. Because of its similarity to rock elm (Ulmus thomasii), this species can be used as a substitute for that species. It is most suitable for the manufacturing of furniture and fence posts. The wood also is excellent for steam bending and therefore is used to make containers such as boxes, baskets, crates, and barrels. Other products made from the wood include caskets and dairy, poultry, and apiary supplies[].

Propagation

Seed - if sown in a cold frame as soon as it is ripe, it usually germinates within a few days[]. Stored seed does not germinate so well and should be sown in early spring[]. The seed can also be harvested 'green' (when it has fully developed but before it dries on the tree) and sown immediately in a cold frame. It should germinate very quickly and will produce a larger plant by the end of the growing season[]. When they are large enough to handle, prick the seedlings out into individual pots and grow them on in the greenhouse for their first winter. Plant them out into their permanent positions in late spring or early summer, after the last expected frosts. Plants should not be allowed to grow for more than two years in a nursery bed since they form a tap root and will then move badly.
Layering of suckers or coppiced shoots[].