The Green Tower Boxwood (Buxus sempervirens ‘Monrue’) is a favored evergreen shrub, known for its distinct columnar shape and adaptability. Its dense, dark green foliage makes it a popular choice for hedges, accents, and formal plantings. This guide helps identify, manage, and prevent common problems affecting Green Tower Boxwoods.
Common Pests Affecting Green Tower Boxwood
Pests can damage Green Tower Boxwoods, affecting their vigor and appearance. Early recognition of infestation signs is key to management. Common pests include boxwood leafminers, boxwood psyllids, and spider mites.
Boxwood Leafminer
The boxwood leafminer is a small midge fly whose larvae feed within leaves. Symptoms include blister-like swellings, leading to yellowing, browning, and premature leaf drop. Pruning infested branches reduces populations. Systemic insecticides or horticultural oil can also offer control.
Boxwood Psyllid
Boxwood psyllids are small, aphid-like insects that cause leaves to cup or curl, often stunting new growth. They produce visible white, waxy secretions. Pruning distorted new growth removes many insects. For severe infestations, insecticidal soap or systemic insecticides may be necessary.
Spider Mites
Spider mites are tiny arachnids, and their damage is apparent. They cause fine stippling on leaves, appearing as tiny yellow or white spots. Heavy infestations show fine webbing and bronze discoloration. A strong water spray can dislodge many mites. Miticides or horticultural oil applications effectively control populations.
Common Diseases Affecting Green Tower Boxwood
Green Tower Boxwoods are susceptible to fungal diseases affecting leaves, stems, and roots. Timely identification of symptoms is crucial for intervention. Sanitation and cultural practices significantly manage these conditions.
Boxwood Blight
Boxwood blight, caused by the fungus Calonectria pseudonaviculata, is a serious disease leading to rapid defoliation and decline. Symptoms begin as dark leaf spots that expand, followed by black streaks or cankers on stems. Infected leaves quickly turn brown and drop, often leaving the plant bare. Immediate removal and destruction of infected plants and debris, plus fungicide applications, prevent its spread. Avoiding overhead watering and ensuring good air circulation also reduces disease pressure.
Volutella Blight
Volutella blight, caused by Pseudonectria buxi, affects leaves that turn dull green or bronze, then tan. Pinkish spore masses may appear on the undersides of infected leaves or stems. This disease can also cause dieback of branches and loose or peeling bark. Pruning affected areas, improving air circulation through thinning, and applying fungicides help manage this issue.
Macrophoma Leaf Spot
Macrophoma leaf spot, caused by Macrophoma candollei, appears as small, circular tan spots with dark borders on leaves. Tiny black dots (pycnidia) are often visible in the center. While not fatal, severe cases can affect appearance. Pruning infected leaves, ensuring good air circulation, and maintaining plant sanitation help control its spread. Fungicidal sprays may be used for widespread or recurring infections.
Root Rot
Root rot, often caused by fungal pathogens like Phytophthora spp., results from poor drainage or overwatering. Affected boxwoods show drought-like symptoms: yellowing leaves, wilting, and stunted growth, leading to decline. Roots appear dark and mushy. Improving soil drainage and adjusting watering practices are crucial for recovery.
Environmental and Cultural Stressors
Green Tower Boxwoods can show distress from environmental conditions or improper care. These non-biological factors weaken the plant, increasing susceptibility to pests and diseases. Addressing them involves adjusting cultural practices to suit the plant’s needs.
Winter Burn
Winter burn occurs when cold winds, sun exposure, and frozen ground cause moisture loss faster than roots can absorb it. Symptoms appear as browning or bronzing of leaves, especially on exposed sides. Adequate fall watering and winter protection, like burlap wraps, prevent desiccation.
Drought Stress
Insufficient water leads to drought stress, especially during dry periods. Signs include wilting, dull foliage, stunted growth, and leaf scorch (brown leaf edges). Consistent, deep watering is essential, particularly for new boxwoods and during prolonged dry spells.
Poor Drainage and Overwatering
Waterlogged soil, often from heavy clay or excessive irrigation, deprives roots of oxygen, leading to problems like root rot. Symptoms include yellowing leaves, wilting, and general plant decline. Improving soil drainage with organic matter and allowing soil to dry slightly between waterings are important.
Nutrient Deficiencies
Nutrient deficiencies hinder healthy growth. Signs include general yellowing of older leaves, pale green foliage, or stunted growth. A soil test identifies specific imbalances like nitrogen or iron deficiencies. Applying a balanced fertilizer based on test results corrects these issues and promotes vigorous growth.
Preventative Measures and Healthy Growth
Maintaining Green Tower Boxwood health is the most effective strategy for minimizing problems. Proactive measures focusing on proper siting, soil conditions, and consistent care build plant resilience. These practices reduce pest infestations, disease outbreaks, and environmental stress.
Proper site selection is foundational for healthy boxwood growth. Green Tower Boxwoods thrive in locations with adequate sunlight (ideally partial to full sun) and good air circulation. Well-draining soil is important, as boxwoods do not tolerate consistently wet conditions. Amending heavy clay soils with organic matter before planting significantly improves drainage.
Effective watering practices are crucial for establishing and maintaining these shrubs. Consistent, deep watering is recommended, especially during the first few growing seasons, allowing the topsoil to dry between applications. Avoiding overhead irrigation minimizes leaf wetness, reducing fungal disease risk. Applying organic mulch around the plant’s base helps retain soil moisture and regulate temperature, but keep it a few inches from the stem.
Fertilization should be guided by soil test results to ensure necessary nutrients without over-application. A balanced fertilizer applied in early spring supports new growth. Pruning techniques, especially thinning, improve air circulation within the canopy, discouraging disease. Removing dead or damaged branches also maintains plant health.
Regular inspection of Green Tower Boxwoods allows early detection of emerging issues. Promptly addressing initial signs of stress, pests, or disease prevents minor problems from escalating. Maintaining a clean garden area by removing fallen leaves and debris contributes to plant hygiene, reducing harborage for pests and pathogens.