Pachysandra terminalis, commonly known as Japanese spurge, is a popular evergreen groundcover celebrated for its deep green foliage and ability to thrive in shady areas. When a patch of this resilient plant begins to turn yellow, it is a clear sign that the groundcover is under stress from an environmental factor, a pest, or a disease. Yellowing, or chlorosis, is the plant’s generalized response to distress, signaling that its ability to produce chlorophyll and photosynthesize has been compromised. Identifying the specific cause of this color change is the first step toward restoring the health of your Pachysandra bed.
Cultural Stressors: Light, Water, and Soil
Improper management of basic needs—light, water, and soil conditions—is one of the most common reasons Pachysandra turns yellow. While this groundcover prefers shade, too much direct sun exposure, particularly the intense afternoon sun, can cause the leaves to bleach or scorch, resulting in a distinct yellow or tan discoloration on the foliage. Protecting the plants from harsh sunlight resolves this yellowing.
Water stress can manifest as yellowing from two opposite extremes: overwatering and underwatering. Overly saturated soil, often due to poor drainage, suffocates the roots by displacing oxygen, leading to widespread yellowing. Conversely, prolonged drought can cause the leaf edges to brown and the entire plant to take on a pale, overall yellow appearance as it struggles to transport nutrients. Ensuring the soil is consistently moist but never waterlogged is important, and amending heavy clay soil with organic matter can significantly improve drainage.
Nutrient deficiencies in the soil also contribute to chlorosis, with two specific elements causing distinct symptoms. A general, pale yellowing of older, lower leaves indicates a lack of nitrogen, a mobile nutrient the plant moves to new growth first. If the newest leaves show yellowing between the veins while the veins remain green, the plant is likely suffering from an iron deficiency, a non-mobile nutrient. A simple soil test can confirm these issues, and a light, annual application of a balanced, slow-release fertilizer can help correct these imbalances.
Insect Pests That Cause Yellowing
Certain insect pests feed on Pachysandra, causing yellowing as a direct result of their sap-sucking activity. The Pachysandra scale, often the Euonymus scale, is a frequent offender that appears as small, waxy, white or brown lumps on the stems and undersides of the leaves. These insects pierce the plant tissue and extract sap, causing the leaves to develop yellow spots or stippling that eventually leads to discoloration and decline.
Spider mites are tiny pests that feed on leaves by puncturing individual plant cells. This feeding damage results in a fine, speckled yellow or bronze stippling across the foliage, which can look like a dull yellowing from a distance. In severe infestations, very fine webbing may also be noticeable on the undersides of the leaves and between stems. Immediate treatment using a horticultural oil or insecticidal soap controls the population.
Fungal and Pathogen Issues
The most destructive disease causing yellowing is Volutella blight, caused by the fungus Volutella pachysandrae. This disease often starts with small, irregular tan or brown spots on the leaves, which expand into concentric rings. As the infection progresses, the leaves turn completely yellow or brown and drop, and brown or black cankers can form on the stems, girdling them and causing the entire shoot to wilt and die.
Volutella blight is considered an opportunistic pathogen, meaning it primarily attacks plants weakened by stress, such as winter injury, drought, or scale insect infestation. It thrives in environments with poor air circulation and prolonged leaf wetness, which are common in dense, mature Pachysandra beds.
Another common issue is root rot, a consequence of persistent overwatering and poor drainage. When the roots decay, the plant cannot absorb water or nutrients, leading to sudden and widespread yellowing, wilting, and collapse of entire sections.
Identifying the Specific Cause and Long-Term Care
Determining the exact cause of yellowing requires careful observation of the location and pattern of the discoloration. If the yellowing is general and uniform across the entire bed, the issue is often cultural, such as too much sun exposure or a widespread nutrient deficiency. Localized yellowing accompanied by distinct spots or cankers on the stems suggests a pathogen like Volutella blight, while small, immobile white or brown bumps confirm a scale insect problem.
Long-term maintenance focuses on reducing plant stress and improving the growing environment to prevent recurrence. Thinning dense patches of Pachysandra periodically improves air circulation and allows the foliage to dry more quickly, defending against fungal diseases. Removing and destroying any infected plant material is an important sanitation practice, as is raking away leaf debris that collects within the bed. Providing a light, balanced fertilizer application in the spring and ensuring consistent, deep watering during dry periods will maintain plant vigor and help the groundcover resist future problems.