Junipers are valued in landscapes for their hardiness and evergreen nature, but browning foliage signals that the plant is under stress. This discoloration is a symptom, not a single problem, and requires immediate attention. Identifying the precise cause is the first step toward recovery, as the remedy for a fungal infection differs significantly from a fix for root damage. This guide offers a systematic way to determine the root of the issue and restore the vibrant green of your juniper.
Environmental and Cultural Stressors
Incorrect watering practices are a leading cause of juniper browning, as both excessive dryness and saturation stress the root system. Junipers prefer deep, infrequent watering. Soggy soil suffocates fine roots, preventing water and nutrient uptake, which mimics drought stress. Conversely, dry weather causes desiccation, turning needles brown when roots cannot supply enough moisture.
Winter desiccation, or winter burn, occurs when frozen ground prevents water absorption while cold winds or bright sun draw moisture from the needles. This results in browning, particularly on the exposed side. Salt damage is often seen near roads or sidewalks treated with de-icing salts. Salt accumulates in the soil or burns the foliage, inhibiting the plant’s ability to absorb water.
Junipers also suffer chronic stress from poor site selection or improper planting. Heavy clay soil with poor drainage is a common issue that predisposes the plant to problems. Transplant shock, where browning occurs shortly after planting, is the plant’s reaction to root disturbance. These stressors weaken the plant, making it susceptible to secondary issues like pests or disease.
Fungal Diseases
Fungal pathogens are a significant source of browning, often manifesting as tip blights. Phomopsis tip blight (Phomopsis juniperovora) primarily attacks the new, succulent growth at the branch tips. Infected new growth turns dull green, then reddish-brown, and finally ash-gray. The fungus is identified by small, black fruiting bodies (pycnidia) appearing on the dead wood.
Kabatina tip blight (Kabatina juniperi) affects older, one-year-old growth. Symptoms appear in late winter or early spring, as the foliage changes color from dull green to red or yellow. This fungus usually requires a wound to gain entry. Both blights create cankers that can eventually girdle and kill the entire branch tip.
Root rot is a serious fungal issue, frequently caused by water mold pathogens like Phytophthora, which thrive in saturated, poorly draining soils. This infection attacks the roots directly, causing them to become mushy and incapable of transporting water. The resulting foliage browning is a secondary symptom of the root system failing, often leading to the rapid decline of large plant sections.
Common Juniper Pests
Several small arthropods cause browning by feeding on the juniper’s sap, primarily the spruce spider mite. This is a cool-season mite whose populations build up in the spring and fall. Mites feed on chlorophyll, causing needles to develop a stippled or bleached appearance.
The “paper test” checks for spruce spider mites: shake a branch vigorously over white paper. If the small specks that fall move, or leave a greenish smear when crushed, mites are present. Fine silken webbing may also be visible in heavy infestations.
Juniper scale is another sap-sucking pest causing browning and loss of vigor. Adult female scales are immobile, appearing as small, circular, waxy bumps adhering tightly to the needles. They extract sap, causing the foliage to lose its luster, turn yellow, and eventually die back.
The bagworm larvae construct protective, spindle-shaped bags from silk and juniper foliage. These bags are carried by the larva as it feeds, causing defoliation. Severe infestations can rapidly strip a juniper of its foliage, resulting in extensive browning and branch dieback.
Practical Steps for Recovery and Prevention
Addressing browning begins with correcting cultural practices, focusing on proper hydration and soil conditions. If the issue is drought, apply deep, infrequent watering to fully soak the root zone and encourage deep root growth. For plants struggling with poor drainage, improving the soil structure or adjusting the landscape to allow water to drain away is necessary to prevent root rot.
For tip blights, sanitation involves careful pruning of all dead and discolored wood. Cut back to healthy tissue and sterilize pruning tools with a bleach solution or alcohol between cuts to prevent spreading fungal spores. Chemical treatments can be used as a preventative measure, with fungicides applied to protect new growth when weather favors fungal development.
Pest control should focus on the specific culprit using targeted applications. Horticultural oils or insecticidal soaps are effective against spruce spider mites and scale crawlers, working by suffocating the pests upon contact. For bagworms, manual removal of the silk bags during the dormant season is highly effective, while a targeted insecticide can be used in late spring when the larvae are small and actively feeding.
Long-term prevention involves planting the juniper in well-draining soil with adequate sunlight. Apply a layer of organic mulch around the base to regulate soil temperature and moisture, keeping it away from the trunk. Avoiding excessive fertilization and shielding plants from winter road salt spray reduces the likelihood of future stress.