Dogwood trees, cherished for their delicate blooms and attractive foliage, are a popular choice in many landscapes. When their leaves begin to turn brown and curl, it often signals an underlying issue, causing concern for gardeners who value these ornamental plants. Understanding the reasons behind these changes is the first step toward restoring your dogwood’s health and beauty.
Understanding Healthy Dogwood Leaves
Healthy dogwood leaves typically exhibit a vibrant green color, feeling smooth and firm to the touch. Their shape is usually oval with pointed tips and distinct veins. These leaves are the primary sites for photosynthesis, the process by which the tree converts sunlight into energy, and also play a role in respiration.
When leaves start to brown or curl, it indicates these vital processes are disrupted. This suggests the tree is struggling. Recognizing these changes early helps identify and address problems before they become severe.
Environmental Stressors Causing Leaf Browning and Curling
Several non-biological factors, often environmental, can cause dogwood leaves to brown and curl. These stressors directly impact the tree’s ability to thrive, manifesting in visible leaf damage. Identifying these triggers helps with accurate diagnosis and effective intervention.
Drought stress causes leaves to curl inward, reducing water loss. Prolonged periods without moisture lead to desiccation, turning leaf edges and tips brown and crispy. This browning, or leaf scorch, results from insufficient water reaching the leaves. Even with moist soil, a tree with a compromised root system may struggle to absorb enough water during dry conditions.
Excessive heat and direct sunlight can inflict damage, leading to sunscald or heat stress. This causes leaves to scorch, browning edges or veins, and a wilted appearance. Dogwoods prefer partial shade, making them susceptible to sun exposure in open landscapes. Newly planted trees are especially vulnerable as their root systems are not yet established.
Transplant shock affects newly planted dogwoods, causing temporary leaf issues as the tree adjusts. Relocation stress can temporarily impair the tree’s ability to absorb water and nutrients, resulting in wilting, browning, or curling leaves. This period requires consistent care to establish strong roots.
Chemical burn contributes to leaf damage when herbicides or excessive fertilizer contact foliage or are absorbed by roots. This can lead to discoloration, browning, and distorted leaf growth.
Common Pests and Diseases
Beyond environmental factors, fungi and insects can cause dogwood leaves to brown and curl. These organisms damage leaf tissue or interfere with the tree’s internal systems. Understanding specific symptoms helps with targeted treatment.
Anthracnose, caused by the fungus Discula destructiva, is a significant dogwood disease, especially in cool, wet weather. Symptoms include tan, blotchy leaf spots with reddish-purple borders, which enlarge rapidly and kill leaves. Infected leaves may blight and remain attached, and the fungus can spread into twigs and branches, causing dieback.
Powdery mildew appears as a white, powdery coating on leaves, particularly new growth. Severe infections can lead to leaf distortion, curling, marginal leaf scorch, reddish discoloration, and premature leaf drop, especially in dense, shady areas with poor air circulation.
Other leaf spot fungi can affect dogwood foliage. These typically cause small, dark brown or purple spots, sometimes with lighter centers or distinct borders. While often cosmetic, severe infestations can lead to premature browning and defoliation, weakening the tree.
Aphids and mites are sap-sucking insects that can cause dogwood leaves to curl, distort, and turn yellow or brown. Aphids extract sap, leading to stunted growth, curled leaves, and honeydew, which attracts sooty mold. Mites feed on leaf tissues, causing stippling, discoloration, and curling.
Effective Solutions and Prevention
Addressing browning and curling dogwood leaves requires immediate solutions and preventative measures for long-term tree health. Many issues can be managed through proper cultural practices, reducing the need for intensive interventions. Consistent care helps dogwoods resist stressors and recover from damage.
Proper watering is foundational, especially during dry spells and for newly planted trees. Dogwoods benefit from deep, slow watering, aiming to moisten soil to a depth of 6 inches, typically once or twice a week during hot, dry weather. This encourages deep root growth, making the tree more resilient to drought. Avoid overhead irrigation, as wet foliage encourages fungal diseases like anthracnose. Apply water directly to the soil around the tree’s base.
Mulching around the tree’s base is beneficial, retaining soil moisture, regulating soil temperature, and suppressing weeds. Apply a 2- to 4-inch layer of organic mulch, such as wood chips or pine straw, keeping it several inches from the trunk to prevent moisture buildup and rot.
Pruning manages pests, diseases, and improves air circulation. Remove dead, diseased, or damaged branches promptly, making clean cuts to prevent further infection. Thinning the canopy enhances air movement, discouraging fungal growth.
For pest management, non-chemical options are often the first defense. Strong water jets can dislodge aphids, and natural predators like ladybugs help control populations. For persistent pest issues, horticultural oils or insecticidal soaps are effective against soft-bodied insects like aphids and mites by smothering or disrupting their membranes. Apply these carefully, avoiding hot, sunny conditions to prevent leaf scorching.
Disease management involves cultural practices, such as raking and disposing of fallen leaves to remove overwintering fungal spores. Fungicides may be recommended for severe fungal diseases like anthracnose or powdery mildew, applied preventatively at bud break or during wet conditions.
Selecting disease-resistant dogwood varieties can significantly reduce future problems. Choosing a planting location with partial shade and well-drained, acidic soil also helps prevent stress. If symptoms persist or worsen, or if you suspect a serious issue like canker, consult a certified arborist. Professionals accurately diagnose complex problems and recommend specialized treatments.