The weeping cherry tree (Prunus pendula) is a celebrated ornamental known for its dramatic cascading silhouette. The health and vibrant color of the foliage are central to the tree’s visual appeal, following the spring bloom. When the typically lush, green canopy displays unnatural discoloration or damage, it signals that the tree is under stress and requires attention. Understanding the characteristics of a healthy leaf and the tree’s natural seasonal changes is the first step in diagnosing deviations in its appearance.
Identifying Weeping Cherry Foliage
A healthy weeping cherry leaf defines its mature summer state. The leaves are simple, arranged alternately along the stem, and feature an ovate to lanceolate shape with finely serrated margins, giving the edges a subtle, toothed appearance.
Individual leaves typically measure between two and four inches long and one to two inches wide. While new spring foliage often emerges with a faint bronze or reddish tint, the mature summer color settles into a consistent, medium to dark green hue. This vibrant green is the benchmark for health before the natural color changes of autumn begin.
The Annual Foliage Cycle
The weeping cherry undergoes natural changes in leaf color throughout the year. The annual cycle begins in early spring, often with the tree’s bloom appearing first, followed closely by the emergence of new leaves (bud break). This initial flush of foliage is typically a lighter, sometimes bronze-green, which complements the blossoms.
As the season progresses into late spring and summer, the leaves darken and stabilize into their deep green photosynthetic phase. This period is when the canopy is densest, providing the full curtain effect of the weeping branches. The summer foliage provides the energy reserves the tree needs to sustain itself and prepare for the following year.
In the autumn, the tree enters senescence, allowing other pigments to become visible. This process causes the leaves to transition from summer green to a spectrum of fall colors. Weeping cherry trees typically display bright yellows and oranges, and some cultivars produce shades of red before the leaves eventually drop.
Diagnosing Leaf Discoloration and Damage
Discoloration outside of the natural fall transition usually points to a pest, pathogen, or environmental problem.
Fungal Diseases
Fungal diseases are common and often manifest as distinct spotting on the leaves. Cherry leaf spot, caused by the fungus Blumeriella jaapii, begins as tiny purple or red spots on the leaf surface. As the disease advances, these spots turn brown or black, and the infected tissue often drops out, leaving a diagnostic “shot-hole” appearance.
Powdery mildew appears as a dusty, white or grayish coating on the leaf surfaces, often causing the leaves to become distorted or curled. Both fungal infections can lead to premature yellowing and leaf loss, weakening the tree over time.
Insect Pests
Pest damage often results in deformed leaves or subtle surface discoloration. Aphids, particularly cherry blackfly, cluster on new growth and the undersides of leaves, sucking out plant sap. This activity causes the foliage to become crumpled and curled. The insects excrete honeydew, a sticky substance that can lead to the growth of black sooty mold.
Spider mites are another common pest; their feeding damage appears as fine yellow stippling or bronzing on the leaves.
Environmental Stressors
Environmental stressors can also cause discoloration, often presenting as a general decline. Heat scorch, which occurs after periods of extreme heat or drought, may result in leaves developing brown edges or an overall scorched appearance, sometimes combined with curling.
Yellowing that is uniform across the leaf or concentrated between the veins (interveinal chlorosis) can indicate a nutrient deficiency, such as a lack of iron or manganese, especially when the tree is planted in soil with a high pH.
Promoting Healthy Leaf Growth
Maintaining a healthy canopy relies on consistent cultural practices that minimize stress and discourage pests and disease.
Cultural Practices
Weeping cherries perform best when situated in a location that receives full sun (at least six hours of direct sunlight daily). Adequate light exposure is necessary for robust photosynthesis and also helps to quickly dry the foliage, which is a primary factor in preventing fungal diseases.
Proper watering is another important element, especially during the tree’s establishment period and in dry weather. The tree requires moist, well-drained soil, and deep soaks every two to three weeks are beneficial during drought. Providing a balanced fertilizer, typically a nitrogen blend, in the spring after the tree has finished blooming supports vigorous growth without encouraging late-season new growth susceptible to winter damage.
Pruning for Air Circulation
Pruning techniques specifically impact leaf health by improving air circulation within the dense, cascading canopy. Thinning out overcrowded inner branches during the dormant season helps reduce humidity around the leaves, making it harder for fungal spores to germinate. It is also important to remove any lower branches that touch the ground, as this contact can provide a pathway for pests and soil-borne pathogens to enter the tree.