Yew plants (Taxus species) are popular evergreen shrubs, valued for their deep green foliage and adaptability. Gardeners often appreciate their dense growth, making them suitable for hedges, topiaries, or foundation plantings. While generally robust, yews can sometimes exhibit browning needles, indicating stress. Identifying the cause is crucial for restoring plant health.
Common Reasons Yews Turn Brown
Browning in yews can stem from various issues, including improper care, environmental challenges, or pest infestations.
Watering Issues
Both excessive and insufficient water can lead to browning yew needles. Yews prefer consistently moist soil but are sensitive to saturated conditions. Prolonged waterlogged soil, especially in heavy clay, can cause root rot, a fungal disease where feeder roots decay, preventing nutrient absorption and leading to browning. Conversely, insufficient watering or drought stress also causes browning, particularly for newly planted yews or during extended dry periods, as the plant cannot access enough moisture.
Environmental Stress
Environmental factors contribute to yew browning. Winter burn occurs when cold winds and sun evaporate moisture from needles while the ground is frozen, preventing water replenishment. Symptoms appear in late winter or early spring, most pronounced on the plant’s south and west sides. De-icing salts are another common culprit; these salts accumulate in soil or splash onto foliage, leading to dehydration and browning, typically visible near salted areas. Transplant shock also causes browning as the plant adjusts to a new environment.
Pests and Diseases
Pests and diseases can cause browning. Pests like mealybugs and scale insects feed on plant sap, causing needles to yellow and brown; mealybugs also excrete honeydew, leading to black sooty mold. Black vine weevil larvae feed on yew roots, impairing water and nutrient uptake, which causes browning. Fungal diseases such as Phytophthora root rot thrive in damp soils, attacking roots and causing needles to yellow and brown. Needle blights, caused by fungi, result in discolored spots, yellowing, and browning of needles, often followed by needle drop.
Nutrient Problems
Nutritional imbalances can cause yew needles to brown. Both deficiencies and excesses of certain nutrients can disrupt a plant’s metabolic processes. A lack of nitrogen, crucial for foliage, can cause yellowing that precedes browning. Conversely, over-application of fertilizer can lead to root burn and subsequent browning. Yews prefer a slightly acidic to neutral soil pH (6.0-7.5); deviations affect nutrient availability.
Normal Needle Shed
Some browning and shedding of inner needles is a natural process for yews. Like many evergreens, yews periodically shed older needles, typically those closer to the plant’s interior. This natural shedding allows the plant to focus resources on new growth. This browning is uniform across older foliage and is not a concern.
Solutions and Prevention for Browning Yews
Addressing browning in yews requires accurate diagnosis and targeted solutions.
Assessing the Damage
Begin by inspecting the affected yew to identify patterns and symptoms. Examine browning needles for their location (inner vs. outer, top vs. bottom), the presence of pests or sticky residue, or any signs of fungal growth. Check soil moisture a few inches below the surface; it should feel moist but not saturated. Observe surroundings for environmental stressors like salted walkways or water pooling. Consider recent changes in watering, fertilization, or transplanting.
Watering Issues
For watering issues, adjust your routine to ensure deep, infrequent watering. Allow the top few inches of soil to dry out before watering again to prevent root rot from over-saturation. If overwatering is suspected, improve soil drainage with organic matter or raised beds.
Environmental Stress
To mitigate winter burn, ensure yews are well-hydrated in the fall before the ground freezes. Burlap barriers can protect plants from harsh winter winds. If salt damage is evident, flush the soil with water in spring to leach salts.
Pests and Diseases
Pest infestations are managed with targeted treatments. For scale or mealybugs, insecticidal soaps or horticultural oils are effective, particularly when applied to the crawler stage. For black vine weevil larvae, parasitic nematodes can be applied as a soil drench. Fungal diseases like needle blight are managed by pruning affected tissues and improving air circulation; fungicides may be used for severe cases. Early root rot may be slowed by improving drainage, but advanced cases often require plant removal.
Nutrient Problems
For nutrient problems, a soil test can determine specific deficiencies or excesses, guiding fertilizer application.
Pruning Brown Sections
Pruning can improve the yew’s appearance and health. Remove dead or severely damaged brown branches by cutting them back to healthy wood; this removes diseased tissue and encourages new growth. While yews tolerate heavy pruning, avoid removing more than one-third of the plant’s canopy in a single season to prevent excessive stress. Minor pruning of damaged branches can be done anytime, but more substantial shaping is best performed in late March or early April before new growth emerges.
Maintaining Healthy Yews Long-Term
Proactive care is essential for the long-term health of yew plants, minimizing future browning issues.
Proper Planting
Proper planting techniques are crucial for healthy yews. Yews thrive in well-drained soil, tolerating a range of soil types from loamy to clay, provided there is good drainage. When planting, dig a hole at least twice as wide as the root ball, ensuring the top of the root mass is level with or slightly above the surrounding soil to prevent root issues. Choose a site with appropriate light, from full sun to full shade, for dense growth.
Watering and Mulching
Consistent watering is vital throughout the year. Established yews require deep watering only during extended dry spells, encouraging root development. Young plants need more frequent watering to establish their root systems, typically once a week for the first year. Apply a 2-3 inch layer of organic mulch around the base to retain soil moisture, regulate temperature, and suppress weeds.
Fertilization
Fertilization supports plant health and vibrant foliage. Apply a balanced, slow-release fertilizer for evergreens in early spring as new growth begins. A soil test can determine the specific nutrient needs of yews, guiding fertilizer choices and application rates. Avoid late-season fertilization, as this can stimulate tender new growth vulnerable to winter damage.
Routine Pruning and Monitoring
Routine pruning maintains the yew’s shape and promotes healthy, dense growth. Annual pruning in late spring to early summer encourages new shoots and a more compact appearance. Remove any dead, diseased, or damaged branches as they appear to prevent problems from spreading. Regular monitoring for early signs of stress, pests, or disease allows for timely intervention.