Northern Whitecedar
Thuja occidentalis · Eastern Arborvitae · Arborvitae · Arbor-vitae · Eastern White-cedar · Northern White Cedar · Swamp Cedar · White CedarUSDA | Grow Zone
3-7Outdoors all year in zones 3 to 7. Anywhere colder, keep it as a houseplant.
- Light
- Full sun to partial shade
- Water
- Once a week deeply
- Humidity
- 40-60%
- Temperature
- 60-75°F (15-24°C)
- Difficulty
- Beginner
- Growth
- Moderate
- Mature size
- 20-40 ft tall
- Pets
- Non-toxic to pets
Thuja occidentalis, commonly known as Northern Whitecedar, is a versatile evergreen tree native to North America. Valued for its attractive foliage and durability, it is often used in landscaping for privacy hedges and windbreaks.
Ask Vesper about Northern Whitecedar
Ideal temperature
60-75°F is where it grows fastest.
Spacing and harvest
- Mature size
- 20-40 ft tall
- Plant apart
- 60-120 in
- Frost
- Hardy: survives frost
Everything it needs
9 essentials at a glance
Watering
Thuja occidentalis prefers consistently moist soil, especially during its first year of growth.
Water deeply once a week, allowing the top 1-2 inches of soil to dry out between waterings. In hot, dry conditions, increase frequency to twice a week. Signs of over-watering include yellowing leaves and root rot, while under-watering may cause browning and wilting of foliage.
Light
This plant thrives in full sun to partial shade, ideally receiving at least 6 hours of direct sunlight daily.
It can tolerate some shade but may become leggy and sparse in low light. For optimal growth, place it in a location that receives morning sun and afternoon shade in hotter climates.
Soil
Thuja occidentalis prefers well-draining, loamy soil with a pH range of 6.0 to 8.0.
A mix of peat, compost, and sand can enhance drainage. Ensure the soil retains some moisture but does not become waterlogged, as this can lead to root rot.
Humidity
This tree prefers moderate humidity levels, around 40-60%.
To increase humidity, consider misting the foliage or placing a humidifier nearby. Signs of low humidity stress include browning leaf tips and excessive needle drop.
Temperature
Ideal temperature range for Thuja occidentalis is 60-75°F (15-24°C).
It is hardy in zones 3-7, tolerating cold temperatures down to -40°F (-40°C). In extreme heat, provide some shade to prevent heat stress.
Fertilizing
Use a balanced fertilizer with an NPK ratio of 10-10-10 or 14-14-14.
Fertilize in early spring and again in mid-summer, following package instructions for application rates. Signs of nutrient deficiency include yellowing foliage and stunted growth.
Pruning
Prune Thuja occidentalis in late winter or early spring before new growth begins.
Use sharp, clean pruning shears to remove dead or damaged branches and to shape the tree. Avoid heavy pruning, as this can lead to a sparse appearance.
Repotting
Repotting is typically not necessary for Thuja occidentalis as it is often grown in the ground.
If grown in containers, consider repotting every 2-3 years or when roots become pot-bound. Signs it needs repotting include roots growing out of the drainage holes and stunted growth. When repotting, choose a pot 1-2 inches larger in diameter and refresh the soil.
Propagation
Propagation can be achieved through stem cuttings or seeds.
For cuttings, take 4-6 inch sections from healthy branches in late spring or early summer. Dip the cut end in rooting hormone, plant in a moist potting mix, and keep in a humid environment until roots develop. Seeds can be sown in spring after stratification.
When it's unhappy
Yellowing leaves
Why it happens
Over-watering or nutrient deficiency
How to fix it
Reduce watering frequency and ensure proper drainage, or apply a balanced fertilizer.
Browning leaf tips
Why it happens
Low humidity or underwatering
How to fix it
Increase humidity levels through misting or a humidifier, and adjust watering schedule.
Root rot
Why it happens
Poor drainage or over-watering
How to fix it
Improve soil drainage, reduce watering, and remove affected roots if necessary.
Pest infestations (e.g., spider mites, aphids)
Why it happens
Dry conditions or stress
How to fix it
Increase humidity, use insecticidal soap or neem oil to treat infestations.
Needle drop
Why it happens
Environmental stress or disease
How to fix it
Ensure proper care, including watering and light conditions, and remove affected branches.
Care through the year
Spring
In spring, apply a balanced fertilizer to promote healthy growth. Check for any winter damage and prune as necessary to shape the plant.
Summer
During summer, ensure consistent watering, especially in hot conditions. Monitor for pests and maintain humidity levels to prevent stress.
Fall
In fall, reduce watering as temperatures drop. Mulch around the base to protect roots from freezing and prepare for winter.
Winter
In winter, protect the plant from harsh winds and extreme cold. Avoid heavy pruning and check for any signs of stress or disease.
Toxicity & Safety
Thuja occidentalis is considered non-toxic to pets and children. However, ingestion of large quantities may cause mild gastrointestinal upset. The foliage is generally safe, but it is best to prevent pets from consuming any plant material.
Good to know
How often should I water my Thuja occidentalis?
Water your Thuja occidentalis deeply once a week, allowing the top 1-2 inches of soil to dry out between waterings, especially during its first year.
Why are my Thuja leaves turning yellow?
Yellowing leaves can indicate over-watering or a nutrient deficiency. Check your watering schedule and consider applying a balanced fertilizer if needed.
What is the best light for Thuja occidentalis?
Thuja occidentalis thrives in full sun to partial shade, ideally receiving at least 6 hours of direct sunlight daily for optimal growth.
When is the best time to prune Thuja occidentalis?
The best time to prune Thuja occidentalis is in late winter or early spring before new growth begins, ensuring a healthy shape and removing any dead branches.
How can I increase humidity for my Thuja?
You can increase humidity by misting the foliage regularly, using a humidifier, or placing a tray of water near the plant to create a more humid environment.
What type of soil is best for Thuja occidentalis?
Thuja occidentalis prefers well-draining, loamy soil with a pH range of 6.0 to 8.0. A mix of peat, compost, and sand can enhance drainage.
Is Thuja occidentalis toxic to pets?
No, Thuja occidentalis is considered non-toxic to pets and children, but ingestion of large quantities may cause mild gastrointestinal upset.
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