The Mr. Bowling Ball Arborvitae, a cultivar of Thuja occidentalis, is a favored evergreen known for its distinctive spherical shape and low-maintenance appeal. It is a popular choice for gardeners seeking year-round interest. However, browning foliage is a common issue that can detract from its aesthetic value. This article explores the reasons behind this discoloration and offers guidance on how to address it.
Understanding Browning in Mr. Bowling Ball Arborvitae
Browning in a Mr. Bowling Ball Arborvitae is typically a symptom of an underlying health issue. While evergreen conifers naturally shed some older, interior foliage, usually in late summer or fall, widespread or rapid browning of outer foliage signals plant stress.
Widespread browning suggests the arborvitae is reacting to unfavorable conditions, such as environmental factors, cultural practices, or biological agents. Early detection of browning, along with observing its pattern and location, provides important clues. Identifying the specific cause is the first step in treating the issue and restoring the plant’s vibrant green appearance.
Common Causes of Browning
Watering Problems
Both insufficient and excessive watering can lead to browning. Under-watering results in dry, brittle foliage, often starting from the tips or outer edges. The soil around the plant will feel dry several inches deep, and browning may progress inward if drought stress continues.
Conversely, overwatering is also damaging, depriving roots of oxygen and leading to root rot. Symptoms often include yellowing foliage before it turns brown, typically starting from the base or inner foliage. The soil will remain consistently soggy, indicating poor drainage or too frequent irrigation.
Environmental Stress
Environmental factors frequently contribute to arborvitae browning. Winter burn occurs when cold winds and bright winter sun cause moisture to evaporate from foliage faster than roots can absorb it from frozen ground. This results in browning on exposed sides. High summer heat and drought conditions can also cause dull, crispy foliage, as the plant struggles to maintain hydration.
Pests
Certain pests can cause browning by feeding on foliage. Spider mites are a common culprit, indicated by fine webbing on branches and a speckled appearance on needles before they turn brown. These pests suck sap, leading to discoloration. Bagworms are another issue; their distinctive spindle-shaped casings can be seen hanging from branches, and their feeding activity defoliates and browns infested sections.
Diseases
Fungal diseases can also lead to browning and decline. Tip blight, a common fungal issue, causes branch tips to turn brown and die back, often appearing in humid conditions. This disease progresses from the branch tips inward, affecting new growth. Root rot, caused by various soil-borne fungi, results from excessively wet conditions and leads to mushy, decaying roots, preventing water and nutrient uptake, leading to widespread browning and eventual death.
Nutrient Issues
Nutrient imbalances, either deficiencies or excesses, cause foliage discoloration. A lack of nutrients like iron can cause yellowing or browning of the needles, indicating chlorosis. Over-fertilization, particularly with high-nitrogen fertilizers, can also damage roots, causing fertilizer burn. This browns foliage as the plant struggles with excess salts.
Transplant Shock
Mr. Bowling Ball Arborvitae, like many plants, can experience transplant shock after being moved. This stress occurs due to root disturbance during transplanting, which temporarily impairs water and nutrient absorption. Browning from transplant shock typically appears within the first few weeks or months after planting, affecting foliage as the plant establishes its roots.
Remedies and Preventative Care
Correcting Watering Practices
Proper watering is fundamental to preventing and resolving browning issues. For Mr. Bowling Ball Arborvitae, check the soil moisture consistently, aiming for the top 2-3 inches to be dry before watering again. Deep, infrequent watering is more beneficial than shallow, frequent watering, as it encourages roots to grow deeper into the soil. Ensuring good drainage is crucial to prevent waterlogged conditions.
Protecting from Environmental Extremes
Shielding your arborvitae from harsh environmental conditions prevents browning. In winter, applying an anti-desiccant spray to foliage reduces moisture loss, and wrapping the plant in burlap protects it from strong winds and intense sun. During hot, dry spells, a layer of organic mulch around the base of the plant retains soil moisture, regulates soil temperature, and reduces heat stress.
Managing Pests and Diseases
Regular inspection for signs of infestation is key to pest management. If spider mites are present, a strong spray of water can dislodge them, and horticultural oil or insecticidal soap apply according to product instructions. Manually remove and destroy bagworms before they cause extensive damage. For fungal diseases like tip blight, improving air circulation and, in severe cases, applying a targeted fungicide is necessary.
Addressing Nutrient Imbalances
If nutrient issues are suspected, a soil test provides information about deficiencies or excesses. Based on the test results, apply appropriate fertilizers to correct imbalances. Use slow-release, balanced fertilizers formulated for evergreens and avoid over-fertilization to prevent harm. Following recommended application rates prevents fertilizer burn and promotes healthy growth.
Ensuring Proper Planting and Aftercare
Correct planting techniques are vital for the long-term health of your arborvitae. Ensure the planting hole is twice as wide as the root ball and only as deep as the root ball, to ensure the plant sits at its original nursery level. Proper soil preparation, including amending heavy clay soils for better drainage, is beneficial. Adequate initial watering immediately after planting and consistent moisture during the establishment period reduces transplant shock.
Pruning Brown Foliage
Once the underlying cause of browning is addressed, pruning can improve the plant’s appearance. Brown or dead foliage can be carefully trimmed back to healthy green growth. This removes unsightly sections and encourages new growth. Use clean, sharp pruning shears for precise cuts, avoiding further stress.
When to Seek Professional Help
If browning is widespread, rapidly worsening, or basic remedies have failed, consult a professional. An arborist or certified landscape professional can diagnose complex issues, such as advanced disease stages or severe root problems, beyond homeowner solutions. These experts provide specialized treatments and management plans.