Arborvitae (white cedar) care

Light

Most houseplants will scorch where arborvitae thrives. Give it the windowsill you'd otherwise leave empty because everything else burned there. Arborvitae grows best in full sun, ideally six or more hours of direct light a day, which keeps the foliage dense and bronze-resistant. It tolerates part shade but thins and becomes leggy in deep shade, opening gaps in a hedge. Indoors a young plant needs the brightest possible window, but it is an outdoor conifer at heart and will decline as a permanent houseplant. A plant moved abruptly from low light to direct sun bleaches in 48 hours — always acclimatise over a week.

Watering

Aim for deeply once or twice a week for the first 1-2 growing seasons, then mainly in droughts for arborvitae, but treat that as a starting point rather than a rule. A south-facing summer windowsill will dry the pot twice as fast as a north-facing winter room. Lift the pot; if it feels noticeably lighter than it did wet, water it. Newly planted arborvitae need consistent, deep watering while roots establish; let the surface dry slightly between soakings but never let the rootball dry out, as drought stress causes browning. Established plants are fairly drought-tolerant but still benefit from a deep soak in prolonged dry spells. Containers dry far faster and may need watering every few days in summer.

Soil and pot

Arborvitae grows best in 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. A pot with a working drainage hole is non-negotiable for this species — even free-draining mix will turn soggy in a closed planter. If you love the look of a decorative pot without a hole, use it as a cachepot around an inner nursery pot you can lift out to water.

Humidity and temperature

Arborvitae sits happiest at around Outdoor ambient humidity and -40 to 30°C (-40 to 86°F). As a hardy outdoor conifer, arborvitae has no specific humidity requirement and copes with normal outdoor air. It dislikes the hot, dry air of heated rooms if grown indoors, where low humidity worsens foliage browning and spider mite outbreaks. If you keep the room above year-round and avoid placing the plant near a cold draught, a hot radiator, or an air-conditioning vent, you have already handled the two biggest indoor stressors.

Fertilising

Feed arborvitae sparingly. Feed in early spring with a balanced slow-release fertiliser or one formulated for evergreens/conifers as new growth begins. Established plants in decent soil need little feeding; avoid heavy late-summer feeding, which pushes soft growth vulnerable to winter burn. Container-grown plants need regular feeding through the growing season. Skip fertiliser entirely on a stressed, recently-repotted, or actively wilting plant — fertiliser salts make damage worse, not better. Wait for a round of healthy new growth before resuming a feeding rhythm.

Common problems

Below are the issues we see most often on arborvitae in the Growli community. Each is annotated with the most common cause so you know where to start.

• 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.
• Spider mites — Hot, dry conditions let spider mites build up and feed on the scales, causing stippling, bronzing and premature needle drop.
• Bagworms — Bagworm caterpillars build silk-and-needle cases that hang from branches and defoliate sections of the plant if left uncontrolled.
• Root rot from waterlogged soil — Heavy, poorly drained or persistently soggy soil suffocates and rots the roots, causing yellowing, dieback and decline.
• Browning from drought stress — Insufficient water, particularly in newly planted specimens or containers, dries the rootball and turns interior and tip foliage brown.
• Bare patches from over-pruning — Cutting back into old, leafless wood leaves permanent gaps because arborvitae does not readily regrow from bare brown stems.

Companion plants

Arborvitae pairs well with boxwood, yew, holly, hydrangea, hosta, and ornamental grasses. These are species with similar light and water needs, so you can group them in the same room or on the same shelf and water as a batch.

Propagation

Propagate from semi-hardwood cuttings taken in late summer to autumn: take 10-15 cm shoots, strip the lower foliage, dip in rooting hormone and root in a free-draining, moist medium in a cool, humid, sheltered spot over winter. Cuttings root slowly. Species plants can also be grown from seed, but named cultivars must be propagated vegetatively to stay true. Propagation is the cheapest, most satisfying way to expand a collection — and it doubles as insurance against losing a mature plant to an accident. Take a backup cutting once the parent is established and healthy.

Toxicity to pets

Arborvitae is toxic to pets. Arborvitae (Thuja) is not listed on the ASPCA toxic or non-toxic plant database, so its safety cannot be confirmed there — and claims that the ASPCA lists it as non-toxic are a misattribution. All parts contain thujone (plus tropolones); thujone is a recognised neurotoxin (the regulated convulsant also found in wormwood and absinthe), most concentrated in the cones, wood and twig tips. Small nibbles typically cause gastrointestinal upset (vomiting, diarrhoea, drooling), but larger ingestions can cause neurological effects including seizures, plus liver and kidney injury; horses, goats and sheep are especially susceptible and serious livestock poisoning is documented. Because authoritative toxicology flags a real systemic hazard, treat arborvitae as toxic: keep clippings away from pets and grazing animals, and contact your vet or a poison control line straight away if any is eaten — do not assume it is pet-safe. If you keep cats, dogs, or curious children in the house, weigh placement carefully — a high shelf or a hanging planter is enough for casual safety. For severe ingestion incidents, call your local vet and the ASPCA Animal Poison Control Center (in the US, 888-426-4435).

Pet-safety status is sourced from the ASPCA Toxic and Non-Toxic Plant List, which catalogues the most-asked-about plants for cats, dogs, and horses.

Arborvitae deep-dive guides

Every aspect of arborvitae care, each with its own calibrated guide:

• Arborvitae watering schedule
• Arborvitae light requirements
• Best soil mix for arborvitae
• Arborvitae fertilizing guide
• When to repot arborvitae
• How to propagate arborvitae
• Arborvitae growth rate & size
• Arborvitae cold hardiness
• Arborvitae temperature & humidity
• Is arborvitae toxic to cats & dogs?

Related guides

Arborvitae is also known as arborvitae, eastern arborvitae, American arborvitae, white cedar, eastern white cedar, northern white cedar, and tree of life.

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