Western Red Cedar (Giant Arborvitae) care

Light

Western Red Cedar needs sun on the leaves, not just bright ambient room light. Grows best in full sun but is one of the more shade-tolerant Thuja species, performing well in partial shade (3–5 hours direct sun). In shadier positions it remains healthy but develops a looser, more open crown. Avoid dense full shade. A south or west-facing windowsill in the northern hemisphere is the default; anywhere else, expect the plant to stretch and pale out within a season.

Watering

Water western red cedar regular — water deeply once or twice a week until established; drought-sensitive. The actual day count varies with pot size, light, and season — the finger test (or lifting the pot to feel its weight) is more reliable than a fixed calendar. Empty any drainage saucer afterwards so the pot isn't sitting in water. Moisture-loving tree native to wet Pacific coastal forests with 1,000–3,000 mm annual rainfall. Young trees require consistent watering; established trees are moderately drought-tolerant but suffer needle browning in prolonged dry spells. Mulch generously around the root zone.

Soil and pot

Western Red Cedar grows best in moist, well-drained to moderately wet, slightly acidic loam or clay loam. Highly adaptable to a range of soil types including clay, loam, and sandy loam; tolerates slightly wet soils better than most conifers. Prefers slightly acidic to neutral pH (5.5–7.0). Avoid extremely dry, sandy, or alkaline soils. Good drainage improves disease resistance. 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

Western Red Cedar sits happiest at around Moderate to high — 55–85% RH humidity and -28°C to 30°C (-20°F to 86°F). Native to high-humidity oceanic environments; performs best where ambient humidity stays above 50%. Foliage can desiccate in very dry, exposed positions or prolonged freezing winds (windburn). Shelter young trees in exposed sites during the first winter. 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 western red cedar sparingly. Not required in fertile garden soils. On poor soils, apply a balanced slow-release conifer fertiliser in early spring. Established trees do not benefit from heavy feeding; excess nitrogen promotes soft growth more susceptible to aphids and Didymascella leaf blight. 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 western red cedar in the Growli community. Each is annotated with the most common cause so you know where to start.

• Didymascella Leaf Blight — A fungal disease causing browning of inner scale leaves and dieback, especially in dense hedging or high-humidity sites with poor air circulation. Improve spacing and prune to open the canopy. Copper-based fungicide sprays in early spring provide protective control.
• Bagworm (Thyridopteryx ephemeraeformis) — Caterpillars construct silk-and-foliage bags, feeding on and defoliating branches. Hand-pick bags from small trees in winter when bags are visible. Btk spray applied at caterpillar hatch in late spring is effective on young larvae.
• Windburn and Winter Desiccation — Exposed plants in zones 5–6 can suffer browning of foliage from cold, dry winter winds drawing moisture from foliage faster than frozen roots can replace it. Apply anti-desiccant spray in late autumn; shelter young trees with burlap windbreaks in their first 2 winters.

Propagation

Most commonly propagated from semi-hardwood cuttings taken in late summer to early autumn: wound the base, apply IBA rooting hormone, and root in gritty peat-free compost under mist or in a humid propagator. Rooting takes 6–10 weeks. Seed germinates readily after 4–6 weeks cold stratification; sow in spring in acidic, moist compost. 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

Western Red Cedar is pet-safe. Thuja plicata is not listed as toxic to cats, dogs, or horses on the ASPCA toxic plant lists. Arborvitae species are generally not considered significantly toxic to pets. The foliage contains thujone, which could theoretically cause mild GI upset if consumed in very large quantities, but ASPCA does not classify this species as toxic. Considered pet-safe; consult a vet if a pet ingests large amounts. 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.

Western Red Cedar deep-dive guides

Every aspect of western red cedar care, each with its own calibrated guide:

• Western Red Cedar watering schedule
• Western Red Cedar light requirements
• Best soil mix for western red cedar
• Western Red Cedar fertilizing guide
• When to repot western red cedar
• How to propagate western red cedar
• Western Red Cedar growth rate & size
• Western Red Cedar cold hardiness
• Western Red Cedar temperature & humidity
• Is western red cedar toxic to cats & dogs?
• Is western red cedar toxic to cats?
• Is western red cedar toxic to dogs?
• Getting western red cedar to bloom

Featured in these plant shortlists

Western Red Cedar qualifies for 12 curated Growli shortlists — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

• Best pet-safe houseplants — Houseplants the ASPCA lists as non-toxic to cats and dogs — every one verified against the ASPCA toxic and non-toxic plant list.
• Best drought-tolerant houseplants — Houseplants that prefer to dry out — forgiving of forgotten watering and ideal for travel or busy weeks.
• Best humidity-loving houseplants — Houseplants that thrive in a bathroom, kitchen, or by a humidifier — selected by documented humidity preference.
• Best flowering houseplants — Indoor plants grown for their blooms — selected from the flowering species in Growli’s plant-care library.
• Best pet-safe low-maintenance plants — Non-toxic to cats and dogs and forgiving of forgotten watering — the easiest safe choices for a busy pet household.
• Best pet-safe flowering plants — Flowering houseplants the ASPCA lists as non-toxic to cats and dogs — colour and blooms in a pet home, without the worry.
• Best pet-safe plants for bright light — Non-toxic to cats and dogs and happy in a bright, sunny spot — safe plants for your best-lit windowsill.
• Best pet-safe large indoor plants — Big, floor-standing houseplants the ASPCA lists as non-toxic to cats and dogs — a statement plant that is safe around pets.
• Best houseplants for full sun — Houseplants that want direct sun — the species for a hot south or west-facing windowsill where shade-lovers scorch.
• Best fast-growing houseplants — Houseplants documented as fast or vigorous growers — quick to fill a pot, cover a pole or trail down a shelf.
• Best cat-safe plants — Houseplants the ASPCA lists as non-toxic to cats (and dogs) — safe greenery for a home with a curious cat.
• Best dog-safe plants — Houseplants the ASPCA lists as non-toxic to dogs (and cats) — safe greenery for a home with a curious dog.
• Browse all 29 plant shortlists — pet-safe, low-light, drought-tolerant and more

Related guides

Western Red Cedar is also known as Western Red Cedar, Giant Arborvitae, Giant Cedar, and Pacific Red Cedar.

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