Emerald Green Arborvitae (Smaragd Thuja) care

Light

Aim for at least 4-6 hours of direct sun on the leaves. Full sun for densest growth and best colour; tolerates partial shade but thins and grows lankier with under 6 hours of direct light. If your only bright window faces south, that's perfect for emerald green arborvitae — same window any aroid would fry on.

Watering

Watering emerald green arborvitae: deeply 2-3 times per week when establishing; weekly once rooted in. The number that matters isn't the day of the week — it's how dry the top 2-3 cm of the pot feels. A finger in the soil tells you more than a watering app. After every watering, tip the saucer. Keep the root zone evenly moist, especially the first two years and during drought. Browning interior foliage often signals drought stress; mulch to conserve moisture.

Soil and pot

Emerald Green Arborvitae grows best in moist, fertile, well-drained loam. Adaptable to a range of soils and pH but prefers neutral to slightly alkaline, consistently moist ground. Avoid both waterlogged and bone-dry sites. 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

Emerald Green Arborvitae sits happiest at around Ambient outdoor humidity humidity and -37 to 32°C (-35 to 90°F). An outdoor hedging conifer unaffected by humidity; good airflow between plants reduces fungal needle blight in humid regions. 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 emerald green arborvitae sparingly. Feed once in early spring with a balanced slow-release or evergreen fertiliser. Newly planted or hedge specimens benefit from a second light feed in early summer; avoid late-season feeding that pushes frost-tender growth. 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 emerald green arborvitae in the Growli community. Each is annotated with the most common cause so you know where to start.

• Winter browning/desiccation — Cold, drying winds bleach foliage; water well before the ground freezes and shelter exposed plantings.
• Interior leaf browning from drought — Insufficient water causes inner foliage to brown and shed; deep, regular watering and mulch prevent it.
• Bagworms — Spindle-shaped silk bags defoliate branches; hand-pick in winter or treat caterpillars in early summer.
• Deer browsing — A favoured deer food; protect with fencing or repellents, especially over winter.

Propagation

Propagated from semi-hardwood cuttings taken in late summer or autumn, treated with rooting hormone under mist or in a humid frame. Cuttings root reliably and stay true to the cultivar; seed does not reproduce the form. 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

Emerald Green Arborvitae is mildly toxic to pets. Thuja occidentalis is not individually listed on the ASPCA toxic or non-toxic plant lists; treat with caution and verify with a vet. The foliage and oil contain thujone, a compound that in quantity can cause drooling, vomiting, diarrhoea, and in severe cases neurological signs in dogs and cats. Reported poisonings are uncommon, but ingestion should be prevented and monitored. 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.

Emerald Green Arborvitae deep-dive guides

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

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

Featured in these plant shortlists

Emerald Green Arborvitae qualifies for 4 curated Growli shortlists — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

• Best drought-tolerant houseplants — Houseplants that prefer to dry out — forgiving of forgotten watering and ideal for travel or busy weeks.
• Best flowering houseplants — Indoor plants grown for their blooms — selected from the flowering species in Growli’s plant-care library.
• 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 houseplants for a cool room — Houseplants that tolerate cool conditions down to about 10°C — for an unheated spare room, hallway, porch or a home kept cool.
• Browse all 29 plant shortlists — pet-safe, low-light, drought-tolerant and more

Related guides

Emerald Green Arborvitae is also commonly called Emerald Green Arborvitae or Smaragd Thuja.

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