Thuja, commonly known as Arborvitae, is a favored evergreen conifer, chosen for its versatility in landscaping. They are widely used for privacy screens, hedges, or as individual specimens. Their hardiness and year-round green foliage make them a reliable option for lasting beauty and structure.
Popular Thuja Varieties
Popular Thuja varieties offer distinct characteristics for various landscaping needs. One widely recognized type is Thuja ‘Green Giant’, a fast-growing hybrid that can reach mature heights of 40-60 feet with a 12-18 foot spread, growing 3-5 feet per year. Its dense, pyramidal habit and dark green foliage make it excellent for tall, rapid privacy screens and windbreaks.
Another common variety is Thuja occidentalis ‘Emerald Green’, also known as ‘Smaragd’. This cultivar grows 10-15 feet tall with a narrow, upright 3-4 foot width. Its vibrant emerald green foliage retains its color well through winter, making it ideal for narrower spaces or formal hedges.
Thuja occidentalis ‘Techny’ is a broad-based, pyramidal evergreen, with rich, dark green foliage that holds its color in colder months. ‘Techny’ matures to 12-15 feet tall and 6-10 feet wide, offering a dense form for privacy screening or as a backdrop.
Planting Thuja
Thuja thrives in full sun to partial shade, ideally receiving at least four hours of direct sunlight daily. Well-drained soil is essential; avoid areas with standing water or heavy clay to prevent root issues.
Prepare the soil by clearing weeds, rocks, and debris, then loosening it to 12 inches deep. Incorporate organic matter like compost or aged manure into the top 12 inches to improve drainage, aeration, and fertility for root development.
Dig the planting hole two to three times wider than the root ball, but only as deep. Ensure the root ball’s top is level with or slightly above the soil line to prevent planting too deeply.
Carefully remove Thuja from its container, gently loosening circling roots if root-bound. Place the tree in the hole’s center, backfill with amended soil, and tamp lightly to remove air pockets. Immediately after planting, water thoroughly to settle soil around roots and deeply moisten the root ball. For hedges, space ‘Green Giant’ Thuja 5-6 feet apart for a dense screen; ‘Emerald Green’ can be spaced about 5 feet apart.
Caring for Thuja
Established Thuja benefit from consistent moisture, especially for young plants and during dry periods. A deep watering once a week, allowing the soil to dry slightly, is sufficient for established trees. Newly planted Thuja may need more frequent watering, sometimes every other day for the first few weeks, gradually reducing frequency as they establish. Avoid overwatering, as saturated soil can lead to root rot.
Fertilization supports healthy growth, especially in early spring as new growth emerges. Apply a slow-release, balanced fertilizer (e.g., 10-10-10 or 14-14-14) once or twice a year, following manufacturer instructions to prevent over-fertilization. Incorporating organic matter like compost enriches the soil with nutrients, improving structure and moisture retention.
Mulching around Thuja retains soil moisture by reducing evaporation and suppresses weed growth. A 2-3 inch layer of organic mulch (e.g., wood chips or shredded bark) regulates soil temperature, keeping roots cooler in summer and warmer in winter, and adds organic matter as it decomposes. Keep mulch a few inches away from the trunk to prevent rot.
Pruning Thuja
Pruning Thuja maintains their shape and size, and removes dead, damaged, or diseased branches. Optimal general maintenance pruning is late winter or early spring before new growth, or early to mid-fall for light shaping. For hedges, light shearing is done during the growing season to maintain a tidy appearance.
Most Thuja varieties do not regenerate new growth from old wood. Avoid cutting into areas lacking green foliage, as bare spots are unlikely to fill in. Focus on trimming the current season’s growth to encourage denser foliage. Sharp, clean pruning shears or hedge trimmers are essential for precise cuts and minimizing plant stress. Remove dead, broken, or diseased branches to maintain plant health and appearance.
Common Thuja Problems
Thuja plants face issues from pests, diseases, or environmental stressors. Spider mites are tiny pests that cause foliage to appear stippled or discolored, leading to a bronzed or brownish appearance. Bagworms are another common pest, creating distinctive, spindle-shaped bags on branches as they feed on foliage. Manual removal of these bags in late fall or early spring helps manage infestations.
Root rot is a concern, caused by overly wet or poorly drained soil. Symptoms include yellowing leaves, wilting, branch dieback, and soggy soil. Proper soil drainage and avoiding overwatering are preventative measures.
Needle blight, a fungal infection, causes brown or yellow spots on foliage and can lead to defoliation. Adequate spacing improves air circulation, reducing fungal disease risk.
Environmental stressors impact Thuja health. Winter burn, characterized by browning foliage, occurs when plants are exposed to harsh winter winds and sun while the ground is frozen, preventing water uptake. Browning also results from drought or overwatering, highlighting the need for consistent moisture. Proper planting site selection and consistent, but not excessive, watering mitigate many common problems.