The Green Mountain Boxwood is a popular choice for many landscapes due to its dense, evergreen foliage and adaptable pyramidal form. While hardy, these shrubs can encounter various issues. Understanding common problems and solutions is important for their health and beauty. Proactive management helps ensure these plants thrive.
Common Pests Affecting Green Mountain Boxwoods
Green Mountain Boxwoods are susceptible to common insect pests that impact appearance and vigor. The boxwood leafminer’s larvae feed inside leaves, causing blistered or puffy leaves, yellow/brown spots, and premature dropping. Adult leafminers are small, mosquito-like flies emerging in spring to lay eggs. Management often involves timed insecticide applications or selecting resistant cultivars.
Boxwood psyllids cause new growth to become distorted and cup-shaped. These small, pale-green insects feed on tender foliage, causing aesthetic damage. Pruning and disposing of affected limbs in mid-May, before nymph maturity, helps control populations. Spider mites can infest boxwoods, leading to stippled, off-color, or bronzed leaves. Thriving in hot, dry conditions, these mites can be managed with miticides for severe infestations.
Diseases of Green Mountain Boxwoods
Green Mountain Boxwoods face several diseases, including Boxwood Blight. This fungal disease, caused by Calonectria pseudonaviculata, leads to distinct leaf spots, rapid browning, and defoliation, starting from lower branches. Symptoms include small, round leaf spots with dark borders and black streaks or cankers on green stems. No cure exists once a plant is infected, making early identification and removal crucial to prevent spread.
Volutella blight, caused by Pseudonectria buxi, is another common fungal disease. Symptoms include yellow to straw-colored leaves, retained on the branch. Pinkish spore masses may be visible on infected leaves and shoots in wet conditions. Pruning infected branches and improving air circulation can help, and fungicides may be used preventatively. Root rot, often caused by Phytophthora species, is a serious issue in wet or poorly drained soils. Affected plants show wilting foliage that turns gray-green to brown, poor growth, and discolored roots and lower stems. Improved drainage is essential, as saturated soil favors this disease.
Environmental and Cultural Stressors
Green Mountain Boxwoods show distress from environmental and cultural factors. Winter burn is a common issue, appearing as reddish-orange, brown, or yellow discoloration on foliage, especially exposed parts. This occurs when plants lose water faster than roots absorb it from frozen ground, exacerbated by drying winter winds and sun. Protecting plants from harsh winter winds and ensuring hydration before winter can mitigate this damage.
Improper watering contributes to problems. Drought stress and overwatering both lead to decline. Drought-stressed boxwoods show yellowing and browning foliage. Conversely, consistently wet or poorly drained soil can cause root rot; boxwoods prefer well-drained conditions.
Overwatering symptoms include yellowing leaves and poor growth. Ensuring well-draining soil and deep watering when the top few inches are dry helps maintain proper moisture. Incorrect planting depth, soil compaction, or insufficient mulching can hinder root development and overall plant health.
Promoting Boxwood Health and Preventing Problems
Maintaining Green Mountain Boxwood health involves proactive measures. Proper site selection is key: these shrubs thrive in partial to full sun (morning sun preferred) and require well-drained soil. Amending heavy clay soils with organic matter improves drainage, preventing root problems. When planting, dig a hole twice as wide as the root ball, ensuring the top is slightly above or at ground level to avoid root rot.
Consistent watering is important, especially during the first growing season, to establish a strong root system. Established boxwoods are drought-tolerant but benefit from weekly watering during dry periods, including winter when the ground is not frozen. Applying a 2-3 inch layer of organic mulch around the base helps retain soil moisture, regulate temperature, and suppress weeds; keep it a few inches from the trunk. Regular, light pruning for air circulation, rather than heavy shearing, reduces humidity within the plant, deterring fungal diseases. Fertilizing lightly in early spring with a balanced, slow-release fertilizer provides nutrients without promoting excessive growth.