Common Name: Rock Elm

General Information

Ulmus thomasii is a deciduous tree with an oblong crown; it can grow up to 30 metres tall[].
The tree is harvested on a commercial basis for its wood, known as 'rock elm'[].
Rock elm wood has long been valued for its exceptional strength and superior quality. For this reason rock elm has been drastically overcut in many localities[].

Known Hazards

None known

Botanical References

, ,

Range

Central and eastern N. America - Minnesota to southern Ontaria and Vermont, south to Arkansas and Tennessee

Habitat

Rich woods and calcareous uplands[]. Dry gravelly uplands, low heavy clay soils, rocky slopes and river cliffs[]. Rocky slopes, limestone outcrops, rich woods, flood plains, stream banks; at elevations from 30 - 900 metres[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Deciduous Tree
Height	30.00 m
Growth Rate	Slow
Pollinators	Wind
Self-fertile	Yes
Cultivation Status	Wild

Cultivation Details

Ulmus thomasii is native to the continental climate of central and eastern N. America, with its cold winters and warm summers. It dislikes maritime climates. It can experience summer temperatures as high as 38°c and winter temperatures as low as -34°c, with a frost-free period ranging from 100 - 200 days[]. Mean annual rainfall can range from 640 - 1,270mm, usually spread through the year.
Prefers a deep fertile soil in full sun[, ], but can be grown in any soil of at least moderate quality so long as it is well drained[]. Plants are tolerant of poor soil conditions in the wild[]. Found in the wild on slightly alkaline to strongly acid soils[].
A very slow growing tree, even in its native range[].
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[].
This species hybridizes with Ulmus pumila and Ulmus laevis[].
The various species of this genus hybridize freely with each other and pollen is easily saved, so even those species with different flowering times can be hybridized[].

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 wood is very strong, hard, heavy, tough, elastic, durable, close and beautifully grained, difficult to split. It weighs 45lb per cubic foot and is used for furniture, general construction, agricultural implements, wheel hubs, as a veneer base, and other purposes demanding toughness, solidity and flexibility[, , , , , , , ].
It is highly shock resistant and has excellent bending qualities which make it good for bent parts of furniture, crates and containers, and a base for veneer. Much of the old-growth was exported for ship timbers[].

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[].