Chinese arborvitae

Chinese arborvitae: how do you recognise it?

Habit

Evergreen conifer, the species up to about 10 m tall and 4 m wide; many garden forms stay rounded or narrow at only 1–3 m.

Foliage

Scale-like and pressed close to the shoots; the flat sprays are vertical, bright green or golden-green.

Cones

At first blue-green, powdery and fleshy, later brown and woody, with prominent hooks on the scales.

Bark

Reddish-brown, peeling in thin strips.

Roots

Shallow to moderately deep; moving it usually works well while it is still young.

Plants: April–May and September–October · Pruning: May–June

Why grow it?

• Compact garden forms stay small and fit small gardens, borders and large pots.
• Evergreen: dense green or golden-green structure all year.
• Tolerates drought and lime better than the western arborvitae.
• Suitable as a specimen, in a hedge or as a ball in a formal planting.
• Little work: it needs hardly any pruning, a light trim of green growth is enough.

Chinese arborvitae: where does it grow best?

• Sun to half shade; in sun it stays densest and the golden-green form colours best.
• Free-draining sandy, loamy or clay soil, acid to very chalky; no permanently wet ground.
• Dry to moderately moist; once established it copes well with drought.
• Sheltered from cold, drying wind. Allow 1–1.5 m for compact garden forms and up to 4 m for the species.

Light

Sun and partial shade

Soil type

Sand, loam or clay

Acidity

Not fussy

Moisture

Dry or normal

Size

10 m tall, 4 m wide

Hardiness

Hardy (to -25 °C)

Goes well with

• Lavender: Loves the same sunny, dry, chalky soil and flowers purple beside the green foliage.
• Rosemary: A fragrant, Mediterranean neighbour for sunny spots.
• Stonecrop: Fleshy leaves and late-summer flower heads in a dry, sunny border.
• Ornamental grasses: Soft tufts that soften the dense, neat shape of the arborvitae.

Chinese arborvitae: when and how to plant it?

Plant in April–May and September–October.

1. Plant in April–May or in September–October, preferably a container or rootballed plant. Never let the rootball dry out.
2. Dig a hole twice as wide as the rootball and just as deep. Loosen the sides with the spade.
3. Set the plant at the same depth as in its pot, with the root collar level with the soil.
4. Backfill, firm lightly and give it a generous watering.
5. Spread wood chips or pine bark around the base, but not against the stems.

Care

Water

In the first year, water generously once a week in dry weather. After that rain is enough; in a pot, water regularly.

Feeding

A little compost or a conifer fertiliser in spring. Not too much: it gives soft, loose growth.

Mulching

A layer of wood chips or pine bark keeps the soil moist and suppresses weeds. Keep it away from the base.

Keeping its shape

Give a light trim in spring and otherwise leave the plant alone.

Moving

This works well while it is still young, provided you take plenty of roots. Older plants move badly.

Tip: Prune only into green, young growth, never into bare brown wood. A light trim at the end of May keeps the ball or hedge neat without bare gaps.

Chinese arborvitae: when to prune it?

Pruning months: May–June.

When: From late May to June, when the young shoots have grown out. At most a second light trim in August.

How:

• Cut only the green, young tips of the sprays, for example to keep a ball or hedge in shape.
• Do not prune too late in the season: late shoots freeze easily.
• Cut dead or damaged branches back to the trunk.
• Wear gloves when pruning, because the foliage can irritate the skin.

Caution: Never cut into old, brown wood without green scales: it will not sprout from it and bare gaps will remain.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Cuttings

In August–September: take 10–15 cm cuttings of semi-ripe shoots, remove the lower leaves and insert them in sandy compost. Rooting takes months.

Seed

Sow outdoors in autumn, or keep the seed moist in the fridge for a few weeks and sow in spring. Garden forms do not come true from seed.

Chinese arborvitae: how does it get through the winter?

Hardy to −25 °C.

• Hardy to about −25 °C: no protection is needed in Flanders.
• Heavy, wet snow can push branches apart: gently shake it off.
• In a pot: put it in a sheltered spot, wrap the pot in hessian and water occasionally in dry, frost-free weather.

Diseases and pests

• Inner browning: In autumn the innermost scales turn brown and drop. This is normal: gently brush out the dead parts.
• Winter damage: Brown tips or dull colour from cold, dry wind or bright winter sun. Shelter helps; cut dead parts away only in spring.
• Root rot: Whole branches turn yellow or brown on wet, heavy soil. Provide free-draining soil; an affected plant usually cannot be saved.
• Tip dieback: Shoot tips turn brown and die, especially in damp, dense plantings. Cut affected parts away in dry weather and allow air and light.

Through the year

• March: Check for winter damage. Cut away dead parts.
• April: Plant. Apply mulch. Give compost or fertiliser.
• May: Plant. Light trim at the end of May.
• June: Light trim of green growth. Water young plants.
• July: Water plants in pots.
• August: Water in dry weather. Optional second light trim. Take cuttings.
• September: Plant. Take cuttings.
• October: Plant. Protect pots for winter.
• November: Shake heavy snow off the branches.
• December: Rest.

Edible and useful

Not edible. All parts of Chinese arborvitae are poisonous if eaten, especially to horses, goats and sheep, but also to dogs, cats and children: the shoots and cones contain essential oils that cause vomiting, stomach ache and, in larger amounts, seizures. The greatest danger is the clippings from a hedge: do not let animals chew shoots or cones, and never throw clippings into a field, run or pen. Wear gloves when trimming, as the foliage can irritate the skin, and wash your hands afterwards. If any is swallowed, call a poison centre (in Belgium 070 245 245) or your doctor at once.

Did you know?

• It used to be called Thuja orientalis; it now has a genus of its own, Platycladus, meaning ‘flat branch’.
• In China it has been a temple and cemetery tree for centuries and is one of the official city trees of Beijing.
• Its seeds are wingless, unlike those of the true arborvitae (Thuja), whose seeds have a small wing.