Nandina shrubs are known for their resilience and attractive year-round foliage, so observing leaf loss can be concerning. However, it is often a diagnosable issue with an identifiable cause. Understanding these reasons can help address the problem and restore the plant’s health.
Normal Leaf Shedding
Some leaf loss is a natural part of a Nandina’s life cycle. As a semi-evergreen shrub, Nandina domestica sheds older leaves, particularly those at the base. This shedding often occurs gradually, with leaves turning yellow or red before dropping, especially during seasonal transitions like autumn and winter. This process allows the plant to refresh its foliage.
Environmental Stress Factors
Environmental conditions significantly impact Nandina health, and unfavorable circumstances can lead to leaf loss. Both overwatering, which keeps soil soggy and causes root rot, and underwatering or drought stress can cause wilting, crispy leaves, and eventual leaf drop. Nandina is drought-tolerant once established, but young plants need consistent moisture.
Temperature extremes are another stressor. Prolonged cold, especially below 10 degrees Fahrenheit, can cause leaf loss. Extreme heat can also lead to leaf browning. Light conditions also influence foliage; intense sun can scorch leaves, while insufficient light results in pale foliage and leaf drop. Protection from cold, drying winds is also beneficial.
Pest Infestations
Pest infestations can weaken Nandina, leading to leaf damage or loss. Spider mites are tiny arthropods that feed on the underside of leaves, causing small white or yellow spots and fine webbing. Infestations are more severe during hot, dry periods.
Aphids can lead to distorted new growth and a sticky honeydew residue, which attracts sooty mold. Large aphid populations can weaken the plant, causing leaves to yellow and drop. Scale insects appear as small bumps on stems and leaves. They feed on plant sap, causing yellowing and eventual leaf drop.
Disease Conditions
Various diseases can affect Nandina, leading to leaf loss and overall decline. Leaf spot fungi cause small, circular spots on foliage that can be brown to dark brown with a reddish halo. These spots can lead to defoliation, especially in humid conditions.
Root rot is a fungal disease occurring when soil is consistently waterlogged. It damages the root system, preventing nutrient absorption, which manifests as yellowing and browning leaves and can lead to plant death. Powdery mildew appears as a white powdery growth on leaf surfaces. Bacterial leaf scorch results in browning leaf margins separated from healthy tissue by a pale band, leading to reduced growth and dieback.
Nutritional Imbalances and Soil Problems
Nutritional imbalances and problematic soil conditions can significantly impact Nandina health, leading to leaf loss. Yellowing of older foliage, slowed growth, and leaf drop can indicate a lack of nitrogen. Iron chlorosis, characterized by yellow leaf tissue with green veins, is another common issue, sometimes caused by high soil pH.
While adaptable, Nandina performs best in loose, fertile, well-drained soil. Incorrect soil pH can hinder nutrient uptake. Nandina prefers a moderately acidic to slightly alkaline soil, with a pH range of 6.0 to 7.5. Poor drainage or compacted soil can also stress the plant by preventing proper root aeration and nutrient absorption.
Actionable Steps and Prevention
To address Nandina leaf loss, begin by inspecting the plant for clues. Examine soil moisture for overwatering or underwatering. Inspect leaves for visual signs of pests like webbing or bumps, and for spots or discoloration indicative of disease.
Adjust the watering schedule, ensuring deep, infrequent watering and allowing soil to dry between applications. If drainage is poor, amend the soil with organic matter or plant in a raised bed. For suspected nutrient deficiencies, a soil test can guide fertilizer application. Protecting the plant from extreme temperatures or providing appropriate light conditions can also alleviate stress. Long-term prevention involves proper planting in well-drained soil, consistent care, and regular inspection to catch issues early.