Japanese zelkova

Japanese zelkova: how do you recognise it?

Habit

Tree of 15–25 m with a short trunk and ascending branches forming a vase; crown about 12 m across.

Leaf

Alternate, 5–12 cm, elliptic with a long pointed tip, singly toothed with 8–14 pairs of regular, sharp teeth; base barely lopsided. Autumn colour yellow to orange-red.

Bark

Smooth and grey with lenticels, like a beech; on older trees flaking in patches with orange-brown blotches.

Flower

Inconspicuous greenish flowers in April, with the leaves.

Fruit

Small, wingless drupes 4–5 mm across.

Difference from field elm

Field elm has a double-toothed leaf with a very lopsided base, and round, winged fruits.

Difference from hornbeam

Hornbeam has a double-toothed, pleated leaf and nutlets on three-lobed winged bracts.

Flowering: April · Pruning: November–March

Identify by feature: Peeling bark

Looks like it, but isn’t

• Field elm Ulmus minor: double-toothed leaf with a very lopsided base, and round, winged fruits. Difference from field elm
• Hornbeam Carpinus betulus: double-toothed, pleated leaf and nutlets on three-lobed winged bracts. Difference from hornbeam

Why grow it?

• An elegant, vase-shaped crown that leaves room underneath for a path or a street.
• Fine autumn colours, from yellow to orange-red.
• Much less susceptible to Dutch elm disease than our elms.
• Copes well with wind and urban conditions.

Japanese zelkova: where does it grow best?

• Full sun.
• Almost any free-draining soil that doesn’t dry out; chalk is no problem.
• Copes well with wind and urban air: a good street and avenue tree.
• Allow for 15–25 m in height and a crown about 12 m across: for a large garden, a park or an avenue.

Light

Full sun

Legal basis

Any garden soil

Moisture

Normal

Size

20 m tall, 12 m wide

Hardiness

Throughout Belgium, no protection needed

Goes well with

• Japanese maple: Fits in the light shade beside the vase-shaped crown; together they give fine autumn colour.
• Japanese cherry: Another Japanese tree, with spring blossom, for an avenue or a large garden.
• Lesser periwinkle: Evergreen ground cover for under the crown.

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

Japanese zelkova: when and how to plant it?

1. Plant from November to March when the ground isn’t frozen.
2. For a street or a narrower spot, choose a cultivar with a narrow vase shape, such as ‘Green Vase’.
3. Put a stake on the windward side and tie the trunk loosely; remove stake and tie after 2–3 years.
4. Water generously after planting and during dry spells in the first two summers.

Care

Watering

In dry spells during the first few years; after that it copes.

Feeding

Not needed.

Formative pruning

Train a young tree to a strong framework: choose a few well-spaced main branches with wide angles.

Checks

On older trees, look out for cracks in narrow forks, especially over paths or car parks.

Tip: Looking for a replacement for an elm in an avenue or on a square? Japanese zelkova has an equally elegant crown and is much less susceptible to Dutch elm disease; choose ‘Green Vase’ if you want a narrower crown.

Japanese zelkova: when to prune it?

Pruning months: November–March.

When: Dead, diseased and broken branches can be removed at any time of year. If pruning is needed, do it during winter dormancy (November–March).

How:

• Little pruning needed. Train a young tree to a strong framework: narrow forks split later on.
• On a young tree, remove competing branches with a narrow fork in good time, while they are still thin.
• A street tree can be crown-lifted gradually in winter.

Caution: Don’t leave formative pruning too late: on an old tree a narrow fork with included bark can no longer be corrected and may split.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Sowing

Sow the fruits outdoors in a seed tray in autumn; they germinate in spring. Cultivars such as ‘Green Vase’ are propagated vegetatively by the nursery.

Japanese zelkova: how does it get through the winter?

Hardy throughout Belgium: no protection needed.

• Fully hardy.
• In winter you recognise it by its vase-shaped crown with fine twigs and its smooth grey trunk.

Diseases and pests

• Narrow forks: Branches with a narrow fork can split later on. Correct this on young trees with formative pruning.
• Dutch elm disease: Much less susceptible than our elms, but not completely immune. If branches suddenly wilt in summer, have the tree checked by an arborist.
• Drought in young trees: A newly planted tree needs water in its first summers, or the leaves shrivel.

Through the year

• January: Formative pruning during winter dormancy.
• February: Formative pruning; planting season when it isn’t freezing.
• March: Last month for formative pruning and planting.
• April: Leaves unfold, with inconspicuous flowers.
• July: Water young trees in dry spells.
• October: Autumn colour: yellow to orange-red.
• November: Planting season; formative pruning possible again.
• December: Formative pruning and crown-lifting during winter dormancy.

What can you use it for?

Garden and landscape

Street and park tree with a vase-shaped crown and fine autumn colours.

Wood

In Japan (‘keyaki’) a valued wood for temples, furniture and taiko drums.

Also used for

Also grown as bonsai.

Did you know?

• A relative of the elm, but much less susceptible to Dutch elm disease; that is why it is often planted where elms once stood.
• In Japan (‘keyaki’) its wood is valued for temples, furniture and taiko drums.
• The name zelkova comes from Georgian, a language of the Caucasus, where a related species grows.