The Arborvitae, a popular evergreen belonging to the Thuja genus, is prized for its dense foliage and conical shape. Often used for privacy screens and hedges, its health and longevity are a major concern for homeowners. Understanding the plant’s natural life cycle and implementing specific care strategies are necessary steps for maximizing its years in a cultivated environment. This article explores the typical lifespan of the arborvitae and provides detailed methods to extend its vitality.
Understanding the Arborvitae’s Natural Lifespan
The potential lifespan of an arborvitae depends significantly on whether it is growing in a landscape setting or its native habitat. Cultivated varieties used for hedging, such as ‘Emerald Green’ or ‘Green Giant’, generally have an expected landscape life ranging from 20 to 40 years. This shorter timeline is often due to environmental stress, improper care, and the plant’s use as a dense, sheared hedge.
Native species exhibit remarkable longevity under ideal, undisturbed conditions. Thuja occidentalis (Eastern Arborvitae) is a very long-lived tree, with some specimens exceeding 1,653 years in age. Thuja plicata (Western Red Cedar) is also known to live for 400 to over 1,000 years in its native Pacific Northwest habitat. This disparity highlights that while genetics provide the potential for long life, cultivation practices and environment determine the lifespan for most landscape trees.
The core factors dictating lifespan include genetic makeup and climate zone suitability. Selecting a cultivar well-suited to the local climate, soil type, and sun exposure is the foundation for a long-lived plant. When planted too close together or in poor soil, trees will struggle to reach their full potential, often declining prematurely due to competition and stress.
Essential Groundwork: Planting and Hydration for Long Life
The most impactful step for arborvitae longevity is correct planting depth, which directly affects the root system’s health. The hole should be dug two to three times as wide as the root ball but no deeper. The root flare, the point where the trunk widens as it meets the roots, must be visible and situated slightly above the surrounding soil level. Burying the root flare is a common mistake that leads to slow decline from suffocation.
Arborvitae are highly susceptible to root rot, making soil and drainage management paramount for long-term survival. They thrive in moist but well-drained soils and cannot tolerate standing water, which starves the roots of oxygen. For heavy clay soils, amending the soil with organic matter like compost can improve aeration and drainage. Planting slightly high, with the root flare exposed, is often the best strategy in poorly draining areas.
Proper hydration management is essential, especially during the first year after planting. Newly installed arborvitae require deep, consistent watering to encourage a robust root system, often needing a deep soak every few days during hot, dry periods. Mature trees are more drought-tolerant but still require supplemental watering during extended dry spells to prevent stress.
Applying a two to three-inch layer of organic mulch around the base of the plant helps regulate soil temperature and conserve moisture. Keep the mulch several inches away from the trunk to prevent moisture accumulation against the bark, which encourages rot and pests. Fertilization is generally minimal for established arborvitae; over-fertilizing, particularly with high-nitrogen products late in the season, can stimulate tender new growth easily damaged by winter weather.
Protecting Arborvitae from Common Threats and Stressors
Specific external threats and biological factors often cut the landscape life of an arborvitae short.
Insect Pests
Among the most common insect problems are spider mites, which are tiny arachnids that feed on the foliage, causing discoloration before browning. Identification often involves looking for fine webbing among the needles. Treatment should focus on specialized products or strong jets of water for minor infestations.
Bagworms are another significant pest. The larvae construct spindle-shaped bags from silk and foliage that hang from the branches. These bags protect the larvae while they feed, leading to defoliation and weakening of the plant. Bags must be manually removed and destroyed before the eggs hatch in late spring.
Fungal Issues
Fungal issues, such as tip blight, cause the green growth at the ends of branches to turn brown and brittle, often starting at the tips and moving inward. This disease is frequently linked to moisture stress. Good cultural practices, like pruning out diseased sections and ensuring proper air circulation, are the primary preventative measures.
Environmental Stressors
Environmental injuries, particularly winter burn, can severely impact the plant’s health and appearance. Winter burn occurs when the evergreen foliage loses moisture through transpiration on sunny or windy winter days, but the frozen ground prevents the roots from replacing that water. Prevention involves ensuring the plant is well-watered late into the fall before the ground freezes, and applying anti-desiccant sprays to the foliage to reduce moisture loss.
Wildlife Deterrence
Wildlife deterrence is a major factor, as deer find the soft foliage of many arborvitae cultivars to be a desirable winter food source. Heavy deer browsing can severely stunt growth and weaken the plant, especially on smaller trees. Simple deterrence strategies, such as applying scent-based repellents or physically netting young trees during the winter months, can protect the foliage and maintain the necessary vigor for a long life.