Laurel varieties, such as Cherry Laurel (Prunus laurocerasus) and Portuguese Laurel (Prunus lusitanica), are valued for their dense, evergreen foliage, making browning leaves particularly noticeable. This discoloration is a common sign of distress, indicating the plant is reacting to an imbalance in its environment or suffering from an infection. The cause is often a correctable issue related to cultural care or localized stressors. Understanding the specific pattern of the browning is the first step toward diagnosing the problem and restoring the plant’s healthy canopy.
Water Management Problems
Improper water delivery is the most frequent cause of brown laurel leaves, manifesting as either underwatering or overwatering. When a laurel experiences drought stress, the leaves often develop dry, crispy edges and tips because the plant cannot supply sufficient moisture to the margins. These leaves may feel brittle and appear wilted as the plant conserves water. To determine if the issue is dryness, check the soil by digging down approximately six inches; if the soil is dry at this depth, deep, thorough watering is necessary.
Conversely, overwatering or poor drainage causes browning by inducing root rot, which mimics drought symptoms. Saturated soil lacks the oxygen necessary for healthy root function, causing roots to decay and making them incapable of absorbing water and nutrients. Leaves may first turn yellow and feel soft or limp before progressing to widespread brown necrosis and branch dieback. Correcting drainage is paramount, often involving the amendment of heavy clay soil with organic material or, in severe cases, replanting in a raised bed. Adjusting watering frequency based on seasonal changes and rainfall is also necessary, ensuring the top layer of soil dries slightly between waterings.
Fungal and Bacterial Infections
Infections from pathogens can cause browning that follows a distinct, identifiable pattern on the foliage. Shot Hole Disease, a common issue for laurels, is caused by either a fungus like Stigmina carpophila or a bacterium such as Pseudomonas syringae. This disease initially presents as small, purplish or brown spots on the leaves, often surrounded by a yellow halo. The infected tissue in the center of the spot eventually dries out and falls away, leaving behind a hole that resembles damage from a shotgun pellet.
Other leaf spots and blights can cause larger, irregular patches of brown or black necrosis, which may lead to premature leaf drop. Good garden hygiene and air circulation are important in managing these issues, as spores and bacteria thrive in moist, stagnant conditions. Pruning out and safely disposing of all affected leaves and branches helps limit the spread of the disease. For persistent or widespread infections, a treatment with a copper-based fungicide or bactericide can be considered, applied according to label instructions.
Environmental and Nutritional Stressors
Browning that appears uniformly across the plant or following a specific weather event often points to environmental stress. Cold damage, sometimes called winter burn or desiccation, is a common problem for broad-leaved evergreens like laurel during winter months. This occurs when the air is cold and windy, causing moisture to evaporate from the leaves faster than the roots can replace it because the soil is frozen. The resulting symptom is browning along the leaf edges and tips, appearing as a scorched margin.
Sun scorch can cause browning on leaves exposed to intense, direct afternoon sun, especially in hot, dry conditions or when the plant is newly planted. The leaves facing the hottest direction may develop large, bleached or brown patches where the tissue has been damaged by excessive heat and light. Nutritional deficiencies can also cause browning, typically starting with chlorosis—a yellowing of the leaf tissue where the veins remain green. This interveinal chlorosis is frequently a sign of iron or manganese deficiency, often because a high soil pH makes the nutrient chemically unavailable for the roots to absorb. A professional soil test can confirm the pH level and nutrient availability, allowing for targeted soil amendments.
Pest Infestation Indicators
While direct pest feeding can create holes and ragged edges, some insects cause browning through sap-sucking or boring, leading to branch and leaf dieback. Scale insects, such as the White Prunicola Scale, attach themselves to the bark and stems, where they feed on the plant’s sap. Heavy infestations are visible as small, waxy, or cottony bumps on the wood, which drain the plant’s resources and cause leaves to yellow, turn brown, and eventually drop off.
Wood-boring insects, like the Peachtree Borer, attack the woody parts of the plant, disrupting the internal flow of water and nutrients. The first visible sign of borer activity is often the browning and sudden death of an entire branch or section of the laurel. Inspecting the lower trunk and main stems for small, oozing holes or the presence of frass (fine, sawdust-like material) confirms a borer infestation. Treating these pests often involves horticultural oils to smother soft-bodied scale insects or targeted, systemic treatments for borers hidden within the wood.