Why is my Thuja turning brown?

It could be due to winter burn, drought, or pest damage.

How often should I water them?

Water deeply once a week during the first year to establish roots.

Plant guide

Arborvitae.

Thuja

Pronounced THOO-yuh

Also known as Arborvitae, Red Cedar, Red-cedars, Thuya, arborvitaes, cedar, thujas, whitecedars

Thuja occidentalis — Photo by Miguel Torres Barrios (CC BY) via iNaturalist

Thuja are popular evergreen conifers known for their dense, scale like foliage and upright growth habit. They work wonderfully as privacy screens or windbreaks in the landscape. These trees are quite hardy and adapt well to many garden conditions.

Another photo of Arborvitae — Photo by Dominique Menard (CC BY) via gbif

At a glance

Care level: Easy
Plant type: Evergreen conifer
Light: Full sun to partial shade
Indoor light: Direct sun
Water: Every 7 to 14 days
Mature size: Varies by species, often 3 to 15 meters
Growth rate: Medium
Hardiness: USDA 2 to 8
Bloom time: Early spring

Care

Keep the soil consistently moist but never waterlogged to ensure healthy growth. Watch for browning foliage, which often indicates drought stress or spider mite activity. Prune lightly in early spring to maintain shape and encourage density.

Watering: Water deeply during dry spells to keep the root zone hydrated.
Feeding: Apply a balanced, slow release fertilizer in early spring.
Pruning: Trim lightly in spring to maintain the desired shape and density.
Repotting: Repot only if the plant is container grown and has become root bound.
Soil: Well draining, fertile loam
Soil pH: 6.0 to 8.0
Temperature: -35 to 30°C
Humidity: 40 to 70%
Drought tolerance: Moderate
Lifespan: Long lived, often 50 to 100 plus years.
Fragrance: Light
Deer and rabbits: Low

Signs it needs repotting

Roots growing out of drainage holes
Water running straight through the pot
Stunted growth

Safety

People: The foliage contains thujone, which can cause irritation or illness if ingested.
Pets: Thuja can be toxic to cats and dogs if ingested, potentially causing digestive upset.
Children: Keep small children away from the foliage as it is toxic if chewed or swallowed.
Contact allergens: Handling the foliage can cause skin irritation or dermatitis in sensitive individuals.
Airborne allergens: The pollen can be a mild respiratory irritant during the spring release.
Edibility: Thuja foliage is toxic if ingested and should never be consumed.

How to identify it

Scale like, overlapping leaves
Flattened, fan shaped branch sprays
Small, woody, oblong cones
Fibrous, reddish brown bark
Dense, conical growth habit

Height: 3 to 15m
Spread: 1 to 4m
Leaves: green, dark green, bronze, evergreen
Flowers: yellow, brown, 0.5 to 1cm
Fruit: brown, Autumn

Problems to watch for

BagwormsCommon
Spider MitesCommon
Root RotUncommon
Twig BlightUncommon

By symptom

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Growing it

Propagation: cuttings, seed
When to plant: spring, autumn
Overwintering: Ensure the soil is moist before the ground freezes. Mulch around the base to protect roots from temperature swings.
In containers: They grow well in large pots for several years, but eventually need to be planted in the ground.

Softwood cuttings

Take 10 cm cuttings in late summer.
Remove lower needles.
Dip in rooting hormone.
Place in a well draining mix.
Keep humid until rooted.

Plant shallow rooted perennials near the base to avoid disturbing the tree roots.

Grows well with

Hostas · They thrive in the partial shade provided by the tree canopy.
Daylily · They add color and contrast to the base of the hedge.

Similar species

False Cypress · Similar evergreen habit but often with more feathery foliage.
Juniper · Similar evergreen structure but with different leaf texture.

Science

Family: Cupressaceae
Genus: Thuja
Order: Pinales
Class: Pinopsida
Native range: North America and Eastern Asia.
Conservation: Not of conservation concern.

These trees thrive in moist, cool climates and often grow in dense, evergreen forests.

Value to wildlife: provides winter shelter for birds, nesting site for songbirds
Pollinators: bees
Uses: privacy screen, windbreak, ornamental hedge, foundation planting

Through the year

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Flowering

Fruiting

Foliage

Ecological indicators

Salinity: 2/9
Soil reaction: 6/9
Light: 6/9
Temperature: 4/9
Moisture: 6/9
Nutrients: 5/9

Taxonomy resolved against GBIF.

Questions people ask

Why is my Thuja turning brown?: It could be due to winter burn, drought, or pest damage.
How often should I water them?: Water deeply once a week during the first year to establish roots.

Where the name comes from

Thuja comes from the Greek word for a fragrant wood, while arborvitae reflects its historical medicinal use.

Good to know

Thuja wood is rot resistant and light.
They are popular for topiary due to their dense growth.
Native Americans used the wood for canoes and the leaves for tea.
The trees can live for hundreds of years in ideal conditions.

Also in

Plants toxic to cats and dogs

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This guide was generated with AI on September 26, 2026 and checked against GBIF taxonomy. It is general information, not horticultural or veterinary advice. Read about how we build these guides.