Chinese elm

Chinese elm: how do you recognise it?

Habit

Small tree of 10–15 m with a rounded crown about 8 m across and fine, slightly drooping twigs.

Leaf

Alternate, 2–5 cm, elliptic with a slightly lopsided base, singly scalloped, leathery and glossy dark green; stays on the tree for a long time in mild winters.

Bark

Flakes off in small pieces, leaving a mosaic of grey, orange-brown and green, as in a plane tree.

Flower

Small, inconspicuous flowers in the leaf axils, in August–September.

Fruit

Small winged fruits about 1 cm long, ripe in October–November.

Difference from field elm

Field elm has a larger, double-toothed leaf with a very lopsided base, and flowers in spring, before the leaves.

Difference from Japanese zelkova

Japanese zelkova has a larger leaf with regular, sharp teeth, and wingless fruits.

Difference from Siberian elm

Siberian elm (Ulmus pumila) is sometimes also sold as ‘Chinese elm’, but it flowers in spring and has coarse, furrowed bark that does not flake.

Flowering: August–September · Pruning: November–February

Identify by feature: Lopsided leaf base · Peeling bark

Looks like it, but isn’t

• Field elm Ulmus minor: larger, double-toothed leaf with a very lopsided base; flowers in spring, before the leaves. Difference from field elm
• Japanese zelkova Zelkova serrata: larger leaf with regular, sharp teeth, and wingless fruits. Difference from Japanese zelkova

Why grow it?

• Beautiful flaking bark with a mosaic of colours.
• Fairly resistant to Dutch elm disease.
• Stays smaller than most elms and fits in a medium-sized garden.
• Takes pruning well: also as a bonsai, indoors or out.

Chinese elm: where does it grow best?

• Sun to partial shade; in sun the crown is densest.
• Almost any soil that doesn’t stay wet for long; also tolerates some drought and urban air.
• About 8 m across: fits as a small tree in a medium-sized garden, or as a street tree.
• As a bonsai: outdoors in a bright spot, or indoors in a bright, cool spot by a window.

Light

Sun or partial shade

Legal basis

Any garden soil

Moisture

Normal

Size

12 m tall, 8 m wide

Hardiness

Throughout Belgium, no protection needed

Goes well with

• Japanese maple: Together they create an Asian feel in the garden, and it is a bonsai classic too.
• Sacred bamboo: A graceful evergreen shrub with red autumn and winter colour for the foot of the tree.
• Japanese holly: A small-leaved evergreen for clipping that takes the shears as well as Chinese elm does.

Good and bad companions

Goes well with

• Tolerate the shade under this tree: oregon grape, rhododendron, oleaster, japanese skimmia, garden privet, camellia, laurustinus, box-leaved honeysuckle

Chinese elm: when and how to plant it?

1. Plant from November to March when the ground isn’t frozen; a pot-grown tree can also go in later, as long as it isn’t freezing or very dry.
2. Dig a generous hole, plant the tree at the same depth as it grew before and firm the soil.
3. Put a stake on the windward side and tie the trunk loosely; remove stake and tie after 2–3 years.
4. Water after planting and during dry spells in the first summers.

Care

Watering

In dry spells during the first few years. A bonsai in a shallow pot needs frequent watering in summer, sometimes daily.

Feeding

Not needed for a tree in the open ground; feed a bonsai every few weeks during the growing season with bonsai fertiliser.

Checks

In June–July, check whether any branches suddenly wilt: even a fairly resistant elm is not immune to Dutch elm disease.

Indoor bonsai

An indoor bonsai wants plenty of light and a cool spot in winter; in a warm, dark room it drops its leaves. Preferably put it outdoors in summer.

Tip: Got a Chinese elm as an indoor bonsai? Put it outdoors in a bright spot from May to October and overwinter it somewhere cool and light: indoors it often gets too little light, and it is really a hardy tree.

Chinese elm: when to prune it?

Pruning months: November–February.

When: In winter (November–February).

How:

• Tolerates pruning well. Train a young tree on a single leader or into an attractive multi-stemmed shape, and remove crossing branches.
• As a bonsai, cut new shoots back to 1–2 leaves once they have 4–6.
• Cut diseased branches well back into healthy wood and disinfect your tools.

Caution: Don’t saw a garden tree in spring or summer: fresh wounds attract the elm bark beetle, which spreads Dutch elm disease.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Cuttings

Semi-ripe cuttings taken in summer root fairly well in a moist propagator under plastic.

Sowing

Sow the winged fruits in autumn, as soon as they are ripe, on the surface of a seed tray.

Chinese elm: how does it get through the winter?

Hardy throughout Belgium: no protection needed.

• Fully hardy in the open ground.
• In mild winters some of the leaves hang on for a long time. A bonsai in a shallow pot freezes faster than a tree in the ground: in hard frost, move it to shelter or to a cool, bright spot indoors.

Diseases and pests

• Dutch elm disease: Fairly resistant, but not immune. If branches suddenly wilt in summer, cut them well back and have the tree checked by an arborist.
• Leaf drop indoors: An indoor bonsai drops its leaves when it has too little light, too much warmth or a dried-out root ball. Move it somewhere lighter and cooler and keep the soil moist.
• Aphids: Aphids on young shoots, especially on an indoor bonsai; hose them off with water or let ladybirds do the work.
• Frozen roots: A bonsai in a shallow pot can be killed by a severe winter. Protect the pot from frost.

Through the year

• January: Pruning, only now in winter; protect a bonsai from hard frost.
• February: Last month for pruning; still planting season.
• March: Planting season; repot a bonsai just before the buds break.
• May: Bonsai: cut new shoots back to 1–2 leaves.
• July: Check for wilting branches (Dutch elm disease); water a bonsai daily.
• September: Flowering: small flowers in the leaf axils.
• October: Winged fruits ripe: sow them.
• November: Planting season; pruning possible again.
• December: Winter pruning.

What can you use it for?

Garden and landscape

Graceful small tree with beautiful bark; also used as a street tree.

Also used for

One of the most popular bonsai species, indoors and out.

Did you know?

• One of the most popular bonsai trees: the ‘Chinese elm’ from the garden centre is usually this species. It is also fairly resistant to Dutch elm disease.
• The species name parvifolia means ‘small-leaved’. It is also known as lacebark elm, after its lace-like, flaking bark.
• It flowers in late summer, whereas our native elms flower as early as February–March, before the leaves.