Repotting guide

When & how to repot Arborvitae (Thuja occidentalis)

Also called arborvitae, eastern arborvitae, American arborvitae, white cedar, eastern white cedar, northern white cedar, tree of life.

More about arborvitae

About Arborvitae

Thuja occidentalis · also called arborvitae, eastern arborvitae · houseplant

Arborvitae is a hardy evergreen conifer grown outdoors for hedging, screening and in large containers. It wants full sun, deep well-drained soil and even moisture while establishing. It is not on the ASPCA list, but its foliage and oils contain thujone — a neurotoxin — so treat it as toxic to pets and livestock and verify any exposure with your vet.

Mature size: Species can reach 12-20 m (40-60 ft) tall and 3-5 m (10-15 ft) wide if unpruned, but is usually kept far smaller as a hedge. Compact cultivars like 'Smaragd' (Emerald Green) mature around 3-4 m (12-14 ft) tall and under 1.2 m (3-4 ft) wide; dwarf forms such as 'Danica' stay under 1 m.

Watch for — Winter burn / foliage bronzing: Cold, drying winds and winter sun pull moisture from the evergreen foliage faster than frozen roots can replace it, scorching it brown, especially on young or exposed plants.

How to tell arborvitae needs repotting

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

Roots poking out of the drainage holes or coiling visibly around the inside of the pot.
You are watering far more often than you used to because the rootball dries out within a day or two.
Water runs straight through and out the bottom without soaking in.
Top growth has slowed or new arborvitae leaves are noticeably smaller than older ones despite good light.

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 arborvitae

Every 12–18 months — sooner if roots show fast. Arborvitae's growth habit — dense, pyramidal to narrowly columnar evergreen conifer with flattened sprays of scale-like, aromatic foliage that is bright green in summer and may turn bronze in winter. branches are erect and spreading, giving the formal, sturdy outline prized for clipped hedges and screens. — sets the pace. Arborvitae is a hardy evergreen conifer grown outdoors for hedging, screening and in large containers. It wants full sun, deep well-drained soil and even moisture while establishing. It is not on the ASPCA list, but its foliage and oils contain thujone — a neurotoxin — so treat it as toxic to pets and livestock and verify any exposure with your vet.

What size pot to step arborvitae up to

Step up one pot size — about 2–3 cm (an inch) wider. Arborvitae grows fast, so it will fill that space within a season, but jumping several sizes at once still backfires: the unused soil stays soggy and rots even a vigorous root system. One size at a time, every year or so, is the rhythm.

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 arborvitae

Early spring, just as new growth restarts, is the ideal window for 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 arborvitae

Time it for spring. Repot arborvitae in early spring as growth restarts so it re-roots quickly into the fresh soil.
Choose one size up. Pick a pot about 2–3 cm wider with drainage holes. One step only — a much bigger pot stays soggy and rots roots.
Ease the plant out. Water lightly the day before, then tip arborvitae out and gently loosen any roots circling the bottom of the rootball.
Repot at the same depth. Put a layer of fresh deep, moist but well-drained loam in the new pot, set the plant so its soil line is unchanged, and backfill, firming lightly.
Water and pause feeding. Water once to settle the soil. Hold off fertiliser for about a month — fresh mix already has nutrients and feeding now burns new roots.

Aftercare

Water arborvitae once to settle the soil, then let the surface dry before watering again — fresh mix around the roots stays wetter than the old compacted ball, so the commonest post-repot mistake is overwatering. Keep it out of direct sun for a week or two while roots re-establish. Do not fertilise for about 4 weeks — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for arborvitae

Arborvitae wants deep, moist but well-drained loam. Thuja occidentalis prefers a deep, fertile, consistently moist yet free-draining soil and is naturally found near streams and damp ground. It tolerates clay and a range of pH (slightly acidic to alkaline) but resents waterlogging, which encourages root rot. In containers use a loam-based mix with added grit for drainage. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting arborvitae — frequently asked questions

How often should you repot arborvitae?

Every 12–18 months — sooner if roots show fast for arborvitae. Repot arborvitae roughly every 12–18 months, in early spring as growth restarts. It grows fast and circles its pot quickly, so step up one size (about 2–3 cm wider) into fresh deep, moist but well-drained loam. Don't jump several sizes — that soggy excess soil is what rots vigorous roots.

What size pot does arborvitae need?

When is the best time of year to repot arborvitae?

Can you put arborvitae straight into a much bigger pot?

No. Even a fast-growing arborvitae should only go up one pot size at a time. A vastly oversized pot holds a reservoir of wet soil the roots cannot reach, which stays cold and soggy and rots the roots — the opposite of what you wanted.

Should you fertilise arborvitae after repotting?

Not immediately. Wait about 4 weeks after repotting 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.