The Oriental Arbor-vitae, Thuja orientalis, is a versatile evergreen conifer. It typically develops a dense, compact, pyramidal or conical shape, reaching heights of 15 to 20 feet in cultivated settings. Its unique scale-like, green to dark green foliage maintains its color year-round. Gardeners utilize Oriental Arbor-vitae as hedges, privacy screens, and specimen plants.
Choosing a Site and Planting
Selecting the appropriate site is important for successful establishment. These evergreens thrive best in full sun, ideally at least six hours of direct sunlight daily, which promotes denser foliage. While they tolerate partial shade, growth may not be as strong.
The soil should be well-drained and consistently moist. Oriental Arbor-vitae adapts to various soil types, including sandy, loamy, or clay soils, if drainage is adequate. An ideal soil pH ranges from slightly acidic to neutral, generally between 6.0 and 8.0.
When planting, prepare a hole two to three times wider than the root ball and just as deep. Ensure the top of the root ball sits level with or slightly above the surrounding ground. Gently loosen roots before placing the tree in the center. Backfill with amended soil, tamp lightly, and water thoroughly to settle the soil. Apply a two to three-inch layer of mulch around the base, keeping it a few inches away from the trunk.
Essential Ongoing Care
Consistent moisture is important for the health of established Oriental Arbor-vitae. Watering once a week is generally sufficient, keeping the soil moist but not waterlogged. During drought or high summer temperatures, increase frequency to every three to four days, providing about one inch of water weekly, adjusted for rainfall.
Deep watering is more beneficial than light applications, encouraging a deeper root system. Check soil moisture by hand; water when the top one to two inches feel dry. Use a soaker hose or allow water to trickle slowly at the base for effective penetration.
Applying a two to three-inch layer of organic mulch around the tree’s base, several inches away from the trunk, helps conserve soil moisture, moderates soil temperature, and suppresses weed growth. This practice also enriches the soil as the mulch decomposes.
Fertilization benefits Oriental Arbor-vitae if growth is slow or foliage lacks vibrancy. Apply fertilizer in early spring, before new growth emerges, or a light application in early autumn. A balanced, slow-release granular fertilizer, such as 10-10-10, is suitable. Spread granules evenly around the plant’s drip line, avoiding direct contact with the trunk. Water thoroughly after fertilizing to dissolve nutrients and prevent root burn.
Pruning Your Arbor-vitae
Pruning Oriental Arbor-vitae maintains its shape, manages size, and removes dead, damaged, or diseased branches. The best time for significant pruning is late winter or early spring, before new growth. This timing minimizes stress and encourages strong new foliage.
Avoid cutting into old, brown, leafless wood, as this evergreen does not regenerate growth from such areas, possibly leaving bare spots. Focus on light shearing of new growth or selective thinning cuts to maintain density and improve air circulation. When removing branches, cut them back to a healthy side branch or the main trunk. To prevent excessive stress, limit foliage removal to no more than one-third of the plant’s total mass in a single season.
Winterizing Oriental Arbor-vitae
Prepare Oriental Arbor-vitae for winter to protect it from damage. Water deeply in late fall before the ground freezes to prevent winter desiccation. Apply a two to four-inch layer of organic mulch around the base, clear of the trunk, for root insulation and moisture retention.
In regions with heavy snowfall, upright varieties are susceptible to branches splaying or breaking. Gently tie branches together with soft twine or fabric straps, spiraling from the base upwards, for support. For protection against harsh winter winds, intense sun, or deer, wrap the tree loosely with breathable burlap. Remove ties or wraps in early spring for healthy growth.
Troubleshooting Common Issues
Browning foliage is a common symptom with various causes. This discoloration may stem from water imbalances, including both underwatering and overwatering. Environmental factors like winter burn, caused by cold winds and frozen ground limiting water uptake, also result in browning. Consistent moisture and proper site selection help prevent these issues.
Pest infestations, such as spider mites, appear as fine yellow speckles on foliage, leading to browning and webbing, especially during dry conditions. A strong spray of water can dislodge them. Bagworms are identifiable by spindle-shaped bags on branches and cause defoliation; these can be handpicked or treated with insecticides in early larval stages.
Fungal diseases like blight cause branch tips to brown and die back. Pruning infected branches, improving air circulation, and avoiding overhead watering help manage these diseases. Root rot, indicated by yellowing leaves, wilting, and mushy roots, results from excessive moisture and poor drainage. Addressing drainage issues and adjusting watering habits are important for recovery.