Repotting guide

When & how to repot Chinese Arborvitae (Thuja orientalis)

Also called Chinese Arborvitae, Oriental Arborvitae, Biota, Oriental Thuja.

More about chinese arborvitae

About Chinese Arborvitae

Thuja orientalis · also called Chinese Arborvitae, Oriental Arborvitae · flowering

Chinese Arborvitae (now often reclassified as Platycladus orientalis) is a versatile, drought-tolerant evergreen conifer from northeastern China and Korea. Its distinctive vertically held, fan-like foliage sprays set it apart from other arborvitaes. Highly adaptable to heat, drought, and alkaline soils, it is widely used in warm-climate hedging, topiary, and specimen planting.

Mature size: 5–15 m tall, 2–5 m wide; growth rate moderate (15–30 cm per year); dwarf cultivars widely available at 0.5–3 m

Watch for — Root Rot (Phytophthora): Phytophthora root and crown rot causes yellowing, wilting, and eventual plant death in poorly drained, wet soils. Ensure excellent drainage at planting; raise beds if necessary. No effective chemical cure once established — prevention through siting is essential.

How to tell chinese arborvitae needs repotting

Repotting on a calendar is less reliable than reading the plant. For chinese arborvitae, watch for these signs:

Thick roots out of the drainage holes, or circling the surface and lifting the plant.
The pot dries out unusually fast and chinese arborvitae wilts between waterings it used to shrug off.
The plant is visibly top-heavy and tips over easily.
Stalled growth and small new leaves over a full season — though with a big specimen, top-dressing is often the better first response before a full repot.

For the underlying biology of a pot-bound root system and why it stalls a plant, see our guide to spotting and fixing a root-bound plant.

How often to repot chinese arborvitae

Every 2–3 years; top-dress in the in-between years. Chinese Arborvitae's growth habit — conical to columnar or irregular evergreen tree or large shrub; distinctive vertically-oriented, fan-shaped foliage sprays (unlike the horizontal sprays of other thuja); scale-like, bright to mid-green leaves; bluish-green ovoid cones — sets the pace. Chinese Arborvitae (now often reclassified as Platycladus orientalis) is a versatile, drought-tolerant evergreen conifer from northeastern China and Korea. Its distinctive vertically held, fan-like foliage sprays set it apart from other arborvitaes. Highly adaptable to heat, drought, and alkaline soils, it is widely used in warm-climate hedging, topiary, and specimen planting.

What size pot to step chinese arborvitae up to

Move up exactly one pot size. A heavy chinese arborvitae dropped into a vastly bigger pot sits in a reservoir of wet soil its roots cannot reach, which rots them and destabilises the plant. In the years between repots, lift off and replace the top 3–5 cm of soil (top-dressing) instead — it refreshes nutrients without the shock of a full repot.

Not sure of the exact diameter? Our pot size calculator takes the current pot and root spread and tells you the right next size — it deliberately recommends a single step up, never a big jump.

The best time of year to repot chinese arborvitae

Early spring, just as new growth restarts, is the ideal window for chinese arborvitae. The plant is moving into its strongest growth phase and re-roots into fresh soil quickly. Avoid repotting in winter dormancy or, for flowering plants, while it is in bud or bloom — recovery is slowest then and you risk dropping the flowers.

Step-by-step: repotting chinese arborvitae

Consider top-dressing first. If chinese arborvitae is not badly root-bound, scrape off and replace the top 3–5 cm of soil instead — far less shock for a big plant that hates moving.
Get help and one size up. For a full repot, choose a pot just one size larger. A heavy plant needs two people and a stable, free-draining pot.
Ease it out on its side. Lay the plant down, slide the pot off, and gently loosen the outer roots. Do not bare-root a mature specimen.
Repot at the same depth. Add fresh well-drained, moderately fertile loam, sandy loam, or clay; tolerates alkaline ph beneath and around the rootball, keeping the original soil line. Firm it so the trunk is stable and upright.
Water and leave it put. Water thoroughly, then leave chinese arborvitae in the same spot and light — moving and repotting at once is what makes it drop leaves.

Aftercare

Leave chinese arborvitae in exactly the same spot and light it was in before — moving and repotting at the same time is what makes a big specimen drop leaves. Water it in well, then let the top of the soil dry before watering again so the larger volume of fresh soil does not stay sodden. Do not fertilise for about 4 weeks — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for chinese arborvitae

Chinese Arborvitae wants well-drained, moderately fertile loam, sandy loam, or clay; tolerates alkaline ph. Unusually adaptable to a wide pH range (5.5–8.0), including alkaline and neutral soils where many conifers fail. Prefers well-drained, fertile soil but tolerates poor and dry conditions. Avoid waterlogged or continuously saturated soils, which lead to root rot. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting chinese arborvitae — frequently asked questions

How often should you repot chinese arborvitae?

Every 2–3 years; top-dress in the in-between years for chinese arborvitae. Fully repot chinese arborvitae only every 2–3 years; in the in-between years just top-dress the top 3–5 cm of soil. Step up one pot size in spring with well-drained, moderately fertile loam, sandy loam, or clay; tolerates alkaline ph. It is heavy and hates being moved, and a vastly oversized pot holds water against the roots and rots them.

What size pot does chinese arborvitae need?

When is the best time of year to repot chinese arborvitae?

Should you top-dress or fully repot chinese arborvitae?

For a big, heavy chinese arborvitae, top-dressing — replacing the top 3–5 cm of soil — is the gentler option most years, with a full repot only every 2–3 years. A mature specimen sulks and drops leaves when fully repotted, so do it as rarely as the roots allow.

Should you fertilise chinese arborvitae after repotting?

Not immediately. Wait about 4 weeks after repotting chinese arborvitae. Fresh mix already contains nutrients, and feeding freshly cut or disturbed roots burns them. Resume your normal feeding routine once you see new growth.