Field elm

Identification and origin

Ulmus minor belongs to the elm family, Ulmaceae. Its native range is very wide: nearly all of Europe, from the Iberian Peninsula, France and Great Britain to Sweden, the Baltic States, Russia and Ukraine; North Africa, from Morocco to Libya; and western and central Asia, from Türkiye and the Caucasus to Iran, Iraq, Kazakhstan and Uzbekistan. It has naturalized in Ireland, the Azores, the Canary Islands, several northeastern US states, Ontario, Bolivia and South Africa. It has carried many names, among them Ulmus carpinifolia and Ulmus procera, the latter used for English elm, now included in this species.

It is a large deciduous tree with an oval, open crown, a straight trunk and slender branches that rise and then arch. It usually reaches 69–88.5 ft tall and 29.5–39.5 ft wide and grows quickly; it takes twenty to fifty years to reach full size.

The alternate, simple leaves are elliptic to ovate, double-toothed, mid to dark green and glossy, and up to 4 in long. They turn golden yellow in fall. In spring, tiny reddish flowers, easy to miss, with male and female flowers on the same tree, come before pale green samaras that are flat and papery, about 0 in across, notched at the tip and holding a single seed.

The twigs are brown to coppery, and some bear corky ridges or warts. The short, hairy winter buds are red-brown to black. On old trees the bark becomes rough and lightly furrowed, broken into small blocks. Cultivars include ‘Jacqueline Hillier’, a slow-growing dwarf, weeping ‘Pendula’ and variegated ‘Variegata’.

Its water-resistant wood has been used in shipbuilding and underwater construction, as well as for furniture, flooring and firewood.

Light

Field elm grows in full sun, with at least six hours of direct light a day, or in partial shade. It handles exposed and sheltered sites alike, facing east, south or west.

Watering

In the ground, once established, it tolerates both drought and short spells of wet soil.

In a container, and especially as bonsai, its needs are much higher. Keep the mix evenly moist, never letting it dry out completely or stay soggy. Check it every day: in strong sun, high heat or during the vigorous spring flush, you might need to water far more often. Avoid watering every day out of habit without checking, though: a waterlogged mix eventually rots the roots.

Potting mix

In the ground it prefers moist, fertile, well-drained soil, whether clay, loam, sand or chalk, and accepts acidic, neutral or alkaline pH. It tolerates urban pollution and salt. In a container, a basic bonsai mix suits it, in a pot with drainage holes.

Temperature

This is a very cold-hardy tree, rated H7, the top hardiness rating, which covers the harshest European continental climates, below -4 °F. It grows in USDA zones 5 to 7 and needs no protection in the ground. In a container, shelter it from freezing winds, which can kill the finest twigs.

Repotting

Grown in a container, its vigorous roots fill the pot quickly, and a pot-bound elm declines: repot in spring, as the buds lengthen, and prune the roots. Young trees in training are repotted every year, older specimens every two to three years.

Pruning

In a garden, field elm needs little pruning: remove dead, damaged or badly placed wood. Make major cuts in early fall, because large wounds made in spring or summer form bulky calluses.

As bonsai, its vigor makes it possible to build fine branching quickly. Let shoots grow three or four nodes, then cut them back to one or two leaves. A healthy tree can be defoliated in midsummer to make wiring easier. A field elm grown from an air-layered branch can become a well-branched bonsai in about ten years, with a yearly pruning in fall once the leaves have dropped.

Propagation

Field elm is propagated from seed, sown outdoors in fall or spring, and from softwood cuttings in summer; hardwood cuttings are taken in winter. Air layering works once the spring growth has firmed up. Chip budding and grafting are also used.

Common problems

• Dutch elm disease: caused by the fungus Ophiostoma novo-ulmi, it is carried by small elm bark beetles that feed on the bark of young twigs, and it also spreads through root grafts between neighboring trees, which is why it moves quickly along hedgerows. In summer, all or part of the foliage yellows, wilts and dries, young shoot tips curl into a shepherd’s crook, and cut wood shows brown streaks. Field elm is not resistant, and no chemical control is practical. The beetles mainly attack elms more than about twenty years old, so young trees and bonsai are far less targeted.
• Elm leaf beetles: these beetles and their larvae chew the foliage.
• Aphids, scale and gall mites: the mites, tiny relatives of spiders, cause galls on the leaves.
• Wood and root diseases: coral spot, honey fungus and Phytophthora root rot in soils that stay too wet.

For all these reasons it is considered a high-maintenance tree. A single symptom can have several causes: look at the whole tree before drawing conclusions.

Toxicity

No toxicity is reported for dogs or cats: field elm does not appear among the plants listed as toxic to these animals. Even so, keep children and pets from chewing on it.