Thuja occidentalis (American Arborvitae)

Thuja occidentalis (American Arborvitae) is a versatile and popular evergreen tree, valued for its ornamental qualities, hardiness, and the benefits it brings to garden landscapes and ecosystems. Its adaptability and ease of care make it a favored choice in many North American gardens and landscapes.

Thuja occidentalis: An In-depth Look

Thuja occidentalis, commonly known as Eastern Arborvitae or Northern White Cedar, is an evergreen conifer well-known for its dense, conical shape and lush green foliage.

Native: Thuja occidentalis is native to North America. It is predominantly found in the northeastern United States and southeastern Canada. This species naturally occurs in wet forests, swamps, and along lake shores, thriving in cool, moist, well-drained environments.

Plant Type and Habit: This species is a coniferous tree with a pyramidal to conical growth habit. It can be single- or multi-trunked and is often used in landscaping due to its dense, evergreen nature.

Size: Slow-growing and long-lived (up to 1,500 years!), Thuja occidentalis can reach 20-40 feet in height (6-12 meters) and 10-15 feet in spread (3-4.5 meters).

Cones: The cone is oblong and light brown, no more than 1/3 to 1/2 inches long.

Foliage: The foliage consists of scale-like leaves in a rich green color, often turning yellowish green to brownish green in winter, particularly if the plant is exposed to winter sun and wind.

Bark: The bark is reddish-brown, fibrous, and peels off in narrow strips.

Uses: Commonly used for hedging, privacy screens, windbreaks, and as ornamental trees in gardens and parks. Also popular for its wood in construction and crafting.

Hardiness: Hardy in USDA zones 2-7, it can withstand cold winters and a range of environmental conditions.

Wildlife: Provides habitat and food for birds and small mammals, particularly with its seeds and as nesting sites.

Toxicity: Generally not toxic to humans or pets, but ingestion of large quantities of foliage can be harmful due to natural compounds present.

Deer and Rabbit: May suffer some damage from deer and rabbits, especially in areas where these animals are prevalent.

Invasiveness: Thuja occidentalis is not considered invasive in its native range, but it should be planted responsibly to avoid overcrowding and competition with other species.

Benefits: Offers year-round greenery, acts as a natural barrier for privacy and wind, and is relatively low-maintenance. It also supports local ecosystems.

American Arborvitae Growing Tips

Light: Thrives in full sun but can also grow well in partial shade. Full sun exposure leads to denser foliage growth. Usually appreciates some light afternoon shade in hot summer climates. Protect from drying winds, especially when young.

Soil: Adaptable to a wide range of soils but prefers moist, well-drained, slightly acidic to neutral soil. Tolerates clay soils.

Water: Regular watering is important, especially for young plants and in dry conditions. Avoid extreme dry soil in the fall, which can cause the evergreen foliage to dry out in winter.

Fertilizer: Apply a balanced, slow-release fertilizer in early spring. Over-fertilization can harm the plant, so follow the recommended rates.

Pruning: Little to no pruning is required. Prune for shaping or size control in late winter or early spring before new growth starts. Avoid heavy pruning.

Mulch: Provide a generous root zone mulch.

Propagation: Propagated through semi-hardwood cuttings in late summer.

Pests and Diseases: Watch for bagworms, spider mites, mealybugs, and scale insects. Leaf tips may suffer damage from leaf miners. Canker can sometimes pose a problem. Fungal diseases like root rot can occur in poorly drained soils. Good air circulation and proper planting depth help prevent these issues.