My Eugenia Topiary Is Losing Leaves
With their dense growth habit and evergreen foliage, Eugenias, including dwarf brush cherry (Eugenia myrtifolia "Compactus") and "Monterey Bay" brush cherry (Eugenia myrtifolia "Monterey Bay"), can be trained as topiaries. Both grow in U.S. Department of Agriculture plant hardiness zones 9 through 11. They are typically problem-free, although some Eugenia topiaries may lose leaves over time. Most causes of leaf loss are minor and treatable, although some may cause irreversible damage and eventual death.
Cultural problems can cause leaf drop in Eugenia shrubs, which is particularly noticeable when they are grown as tightly pruned, manicured topiaries. The wrong watering, sun exposure or temperatures below 32 degrees Fahrenheit are all common causes of leaf loss in Eugenia topiaries, but soluble salt buildup from hard water or may also cause premature leaf loss. Other symptoms include wilting and a chlorotic, or yellow, appearance along the central rib of otherwise healthy leaves, as well as burned leaf edges and branch death.
Correcting underlying cultural problems will reverse most instances of leaf loss in Eugenia topiaries, although it may take time for the new growth to emerge. Eugenia shrubs perform best when grown in full sun with some light afternoon shade in hot, dry inland climates. A sudden change in sun exposure will cause stress-related leaf loss, so avoid moving the topiary to a radically different light exposure. Water deeply whenever the soil feels dry in the top 1/2 inch and use distilled or filtered water with a low mineral content to prevent salt buildup on the soil surface. If salt buildup occurs, flush the soil with fresh distilled water and avoid applying fertilizer for at least one month.
One of the most devastating causes of leaf loss in Eugenia topiaries is branch dieback, which is an infection caused by the fungus Neofusicoccum parvum. It happens mostly in late summer when temperatures are at their peak and wanes as the weather cools. Infected shrubs develop crisp, brown foliage that will persist for a week or so before dropping, as well as reddish discolorations at the base of the branches. No surefire treatment exists for branch dieback, so prevention and palliative care are key.
Treatment and Prevention
Healthy, stress-free Eugenia topiaries are less likely to develop infections like branch dieback, so providing the right growing conditions and care is crucial. Space the topiaries at least 4 to 6 feet apart to limit the chances of infection, and avoid splashing water on the foliage because excess moisture provides a prime environment for fungal growth. If symptoms occur, the infected branch should be pruned 4 inches below the symptomatic portion using freshly sanitized pruning shears, and the shears should be cleaned with a 25 percent bleach solution after use to keep the infection from spreading. Discard the pruned Eugenia branches rather than using them as mulch or compost.
Pest infestations seldom cause serious damage to healthy Eugenia topiaries. Already stressed shrubs may attract an insect colony large enough to cause leaf drop or other worrying symptoms. California red scale (Aonidiella aurantii) and woolly whitefly (Aleurothrixus floccosus) are two common culprits behind leaf drop in Eugenia topiaries. In addition to leaf drop, they may also cause deformed leaves, stunting and reduced vigor. Woolly whiteflies produce distinctive white, cottony masses on the undersides of the leaves.
Treatment and Prevention
Good cultural practices will reduce the chances of a serious pest infestation both by limiting stress to the Eugenia topiary and by creating unsuitable conditions for insects to breed and feed. Once an infestation occurs, the mode of treatment varies according to the type of insect. California red scales can be controlled by spraying the leaves thoroughly with a ready-to-use insecticidal soap at two-week intervals until the problem subsides. Woolly whiteflies are harder to control once a large colony is established, so limiting their numbers is crucial. A combination of mulch, traps and manual removal is best for adult whiteflies, while the pupae can be controlled by applying insecticidal soap weekly until their numbers decline.
Samantha McMullen began writing professionally in 2001. Her nearly 20 years of experience in horticulture informs her work, which has appeared in publications such as Mother Earth News.