Key Facts
- Evergreen conifer with scale like foliage
- Native to northeastern North America
- Commonly used for hedges screens windbreaks and specimen plantings
- Mature trees frequently reach dozens of feet tall in natural stands
- Tolerates moist and poorly drained soils better than many conifers
- Wind pollinated with small inconspicuous cones in spring
- Propagated by seed and easily by cuttings for many cultivars
Northern Whitecedar (Thuja occidentalis) is an evergreen conifer native to northeastern North America with dense scale-like foliage and small spring cones. It is prized for formal hedges, screens, windbreaks and specimen plantings while cultivars vary from dwarf garden forms to tall trees found in natural stands.
Identification
Evergreen with flattened sprays of scale-like leaves and small inconspicuous seed cones produced in spring. In native stands the species commonly reaches roughly 40 to 60 feet tall with a crown spread often near 10 to 15 feet, while many cultivated varieties are much smaller or more columnar.
Best uses and where to grow
Used widely for hedges, screens, windbreaks and specimen plantings because of its dense foliage and tolerance for moist sites. Performs in full sun to part shade and is commonly listed as hardy to about USDA zones 2 to 7, with some cultivars extending into warmer zones; exposed cold sites can increase winter dieback risk.
Planting and spacing
Place specimen trees where a mature spread of 10 to 15 feet is acceptable; select narrower or dwarf cultivars for tighter spaces or formal hedges. Plant on sites with adequate moisture and allow room for root and crown development to reduce competition and long term maintenance needs.
Watering and soil
Prefers moist, fertile soil and tolerates poorly drained and heavier clay soils better than many conifers. Recommended soil pH is roughly 5.5 to 7.5. Avoid prolonged drought which stresses foliage; in containers ensure good drainage to prevent root rot and decline.
After flowering and pruning
After spring cone production inspect for winter or drought damage and prune to maintain shape. Many cultivars respond well to formative pruning for hedges and screens; avoid removing large amounts of older wood that lacks green foliage because recovery from cutting into bare wood is slow.
Controlling spread and maintenance
Not known for aggressive naturalizing; mature trees occupy a predictable footprint so control is mainly by pruning and cultivar choice. Routine trimming keeps hedges dense and reduces lower-branch loss. Monitor for reduced vigor in prolonged drought or when planted in full shade.
Propagation
Propagated by seed and commonly by softwood or semi-ripe cuttings, layering and grafting for named cultivars. Cuttings preserve cultivar characteristics while seed can produce variable offspring. Rooting success and best timing vary by cultivar and local climate.
Containers and urban planting
Choose dwarf or columnar cultivars if planting in containers or tight urban sites because the species can reach many feet when mature. Containers must drain well and avoid persistent waterlogging; larger container volume reduces stress during dry periods.
Toxicity and wildlife
Contains volatile essential oils including thujone that can cause gastrointestinal and neurological symptoms if ingested by pets or livestock and may irritate sensitive skin. Severity depends on amount eaten; consult local poison control or a veterinarian for suspected ingestion or specific treatment advice.
Frequently asked questions
- How fast does Northern Whitecedar grow?
- Growth rate varies by cultivar and site. The species can reach roughly 40 to 60 feet in native stands, while cultivated forms range from slow-growing dwarfs to faster, taller types depending on conditions.
- What soil does it prefer?
- Thrives in moist, fertile soils and tolerates heavier, poorly drained clay; prefers a roughly neutral to slightly acidic pH around 5.5 to 7.5.
- Is it suitable for hedges?
- Yes. Dense foliage and tolerance of pruning make it a common choice for hedges and screens. Use cultivars selected for narrow habit for tighter spaces.
- Are Northern Whitecedar trees toxic to pets?
- Thuja species contain volatile oils that can cause vomiting, diarrhea and neurological signs if ingested. Contact local poison control or a veterinarian for guidance after exposure.
- How do I propagate Northern Whitecedar?
- By seed or vegetatively using softwood or semi-ripe cuttings, layering and grafting. Cuttings maintain cultivar traits and are commonly used for named varieties.
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