Cherry laurels are popular evergreen shrubs, but browning leaves indicate underlying issues. Identifying the cause is crucial for restoring plant health.
Understanding Why Cherry Laurel Leaves Turn Brown
Cherry laurel leaves turn brown due to various factors, from environmental conditions to pests and diseases. Identifying the cause is essential for effective intervention.
Environmental Stress
Improper watering, both insufficient and excessive, frequently causes browning leaves. Underwatering leads to drought stress, drying and browning leaves from the tips or edges; conversely, overwatering or poor drainage causes root rot, depriving roots of oxygen and leading to yellowing, then browning, and leaf drop. Cherry laurels do not tolerate compacted, poorly draining clay soil.
Temperature extremes also contribute to browning. Winter damage from drying winds, low temperatures, or late frosts can brown and embrittle leaf tips or edges. Heat stress and sun scorch, especially in full sun with reflected heat, can cause widespread browning and plant decline.
Pest Infestations
Certain pests can brown cherry laurel leaves. Scale insects, like white prunicola scale, feed on plant sap, causing leaf yellowing, browning, and branch dieback; they appear as white, crusty coverings on stems and branches. Peachtree borers also cause branch dieback and leaf browning, leaving small holes and sawdust near stem bases.
Fungal and Bacterial Diseases
Fungal and bacterial pathogens impact leaf health, leading to browning. Cherry Shot Hole disease, caused by Xanthomonas pruni or Blumeriella jaapii, results in reddish-brown spots that dry and fall, creating a “shot-hole” appearance. Powdery mildew, a fungal disease, initially appears as faint yellow/brown patches or a white powdery coating, with affected areas later browning and developing irregular holes. Root rot, often linked to overwatering, is a serious fungal issue causing leaves to yellow, brown, and fall as branches die back.
Nutrient Deficiencies
Lack of essential soil nutrients can manifest as leaf discoloration, including browning. Iron deficiency, for instance, can yellow leaves while veins remain green, eventually progressing to browning. Soil pH plays a role; too much lime can prevent nutrient absorption, leading to chlorosis and subsequent browning. General nutrient deficiencies can result in stunted growth and leaf discoloration.
Pruning Stress
Improper or aggressive pruning can stress cherry laurels, leading to browning. Shearing, for example, creates an outer layer limiting air circulation and light penetration, making the plant more susceptible. Cutting leaves in half with hedge trimmers can also result in unsightly brown edges. Incorrect timing or injuring leaves during pruning can also cause browning.
Effective Solutions and Prevention Strategies
Addressing browning cherry laurel leaves involves corrective and preventative measures.
Addressing Environmental Stress
Proper watering is paramount; cherry laurels need consistent moisture but not waterlogged conditions. During dry periods, especially in the first two years, water deeply at the base once a week to ensure moisture reaches deeper roots. In winter, reduce watering frequency but don’t let soil dry out completely, as evergreens lose water through leaves. Ensuring good drainage by amending heavy clay soils with organic matter like compost or sand prevents root issues.
Protecting plants from temperature extremes also minimizes browning. In cold climates, a protective burlap screen shields shrubs from drying winter winds and sun scorch. For heat stress, select a planting location that avoids reflected heat from buildings or pavement.
Managing Pest Infestations
Early detection is key for pest control. Regularly inspecting cherry laurels for scale insects, like white crusty coverings on branches, allows prompt action. For small infestations, scales can be scrubbed off with a soft brush and soapy water. Horticultural oils applied during dormancy can suffocate overwintering scale eggs and vulnerable crawlers. For borers, maintaining plant vigor through proper care helps prevent attacks; cut and dispose of affected branches.
Treating Fungal and Bacterial Diseases
Controlling fungal and bacterial diseases often involves improving cultural practices. To prevent Cherry Shot Hole and powdery mildew, avoid overhead watering to minimize leaf wetness and ensure good air circulation by avoiding overcrowding. Promptly remove and destroy infected leaves or plant debris to prevent spore spread. While fungicides are available for some fungal issues, cultural practices are often sufficient; chemical controls are generally not recommended for bacterial shot hole. Disinfecting pruning tools between cuts helps prevent disease transmission.
Improving Soil and Nutrition
Regular soil testing provides valuable pH and nutrient level information, guiding amendments. Cherry laurels prefer well-drained, fertile soil with a slightly acidic to neutral pH, ideally between 6.0 and 7.5. Amending soil with organic matter like compost improves drainage, water retention, and nutrient content. If a nutrient deficiency is identified, apply a slow-release, balanced fertilizer in early spring to support healthy growth. Avoid late-season nitrogen fertilization, which can promote tender new growth susceptible to frost damage.
Proper Pruning Practices
Correct pruning techniques minimize stress and promote healthy growth. The best time for general pruning is late winter or early spring before new growth, or immediately after late spring/early summer flowering. Remove any dead, diseased, or damaged branches back to healthy wood. When shaping, use hand pruners to avoid cutting leaves in half, which can look unsightly. For hedges, prune with a slightly wider base than top to allow light to reach lower foliage and ensure good air circulation.
When to Seek Expert Assistance
While many cherry laurel issues can be managed with proper care, professional help is sometimes advisable. If browning leaves persist despite diligent application of these strategies, or if the plant shows rapid decline, it may indicate a more complex problem. Large-scale pest infestations or widespread disease unresponsive to typical treatments also warrant expert evaluation. Consulting a certified arborist or plant pathologist can provide an accurate diagnosis and tailored treatment plan for severe or unusual symptoms.