Japanese Arborvitae (Standish's Arborvitae) care

Light

Japanese Arborvitae needs sun on the leaves, not just bright ambient room light. Requires full sun to partial sun — a minimum of 5–6 hours of direct light daily for best form and density. In its native subalpine habitat it receives high light intensity. Partial shade is tolerated, especially in hot climates, but reduces vigour and crown density. 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 japanese arborvitae regular — keep soil evenly moist; do not allow to dry out completely. 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. Prefers consistently moist, well-drained soil; sensitive to both prolonged drought and waterlogging. Water deeply once or twice weekly during dry periods, especially in the first 3 years of establishment. Avoid overwatering in poorly drained soils, which promotes root rot.

Soil and pot

Japanese Arborvitae grows best in moist, well-drained, slightly acidic loam or sandy loam. Grows best in fertile, humus-rich, slightly acidic soils (pH 5.5–7.0) with consistent moisture. Tolerates a range of well-drained soil types but dislikes compacted, waterlogged, or strongly alkaline conditions. Incorporate organic matter at planting to aid moisture retention and 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

Japanese Arborvitae sits happiest at around Moderate to high — 50–75% RH humidity and -28°C to 28°C (-20°F to 82°F). Native to cool, humid Japanese mountain forests. Performs well in moderate to high humidity environments. Tolerates cool, moist oceanic climates well. May suffer foliage desiccation in hot, dry, exposed positions; shelter from harsh drying winds, especially in 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 japanese arborvitae sparingly. Light annual feeding is sufficient. Apply a balanced slow-release granular fertiliser in early spring. Japanese Arborvitae is slow-growing and does not require heavy nutrition. Overly fertile soils can promote rank, soft growth. Established trees growing in good garden soil rarely need supplemental feeding. 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 japanese arborvitae in the Growli community. Each is annotated with the most common cause so you know where to start.

• Root Rot in Wet Soils — Phytophthora cinnamomi and related water moulds cause crown and root rot in waterlogged conditions. Japanese Arborvitae is sensitive to prolonged wet feet. Ensure excellent soil drainage at planting; avoid low-lying areas. Raise planting beds if drainage is poor.
• Scarcity and Availability — Thuja standishii is rarely stocked by mainstream nurseries and can be very difficult to source in the US or UK. Specialist conifer nurseries or botanical garden plant sales are the most reliable source. Plants sold as 'Green Giant' are a related hybrid (T. standishii × T. plicata), not the pure species.
• Spider Mites in Dry Conditions — Hot, dry weather encourages spider mite infestations, causing bronzing and dull foliage. Increase irrigation frequency during heat spells; apply neem oil or insecticidal soap to foliage undersides at the first sign of infestation. Good air circulation also reduces risk.

Propagation

Semi-hardwood cuttings taken in late summer root reliably under mist with IBA rooting hormone treatment: wound the stem base, insert in gritty, well-drained compost, and maintain humidity for 6–10 weeks until rooting. Seed propagation is possible with 4–6 weeks cold moist stratification followed by spring sowing, but seed can be difficult to obtain. Grafting onto Thuja occidentalis rootstock is used commercially. 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

Japanese Arborvitae is pet-safe. Thuja standishii is not individually listed by the ASPCA, but arborvitae species (Thuja genus) are not classified as toxic to cats, dogs, or horses on ASPCA toxic plant lists. Foliage contains low levels of thujone, but ASPCA does not flag the genus as toxic. Considered pet-safe; monitor pets if large quantities are ingested and consult a vet if symptoms arise. 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.

Japanese Arborvitae deep-dive guides

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

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

Featured in these plant shortlists

Japanese Arborvitae 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 fragrant houseplants — Indoor plants with scented flowers or aromatic foliage — greenery you can smell, selected from our care library.
• 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

Japanese Arborvitae is also commonly called Japanese Arborvitae or Standish's Arborvitae.

• Salvia farinacea 'Strata' care — light, water and common problems
• Celosia argentea var. cristata 'Chief Mix' care — light, water and common problems
• Celosia argentea var. plumosa 'Fresh Look Yellow' care — light, water and common problems
• All 6887 plant care guides in the Growli library