Maryland Grows

Q: My cherry laurels do not look good. There are brown spots and holes on the leaves and white stuff on the trunk. What can I do?

A: First, there is a lot to like about cherry laurels (Prunus laurocerasus). They are popular evergreen screening and foundation plants, deer-resistant, and pretty tough once established. Cherry laurels make their best growth in moist, well-drained soil in full sun to partial shade. They even tolerate full shade.

We receive numerous questions about problems with these shrubs. They can have multiple issues that are attributed to environmental, climate, or site conditions. When the plants are stressed, they weaken and become susceptible to diseases and/or insect pests. It is helpful to be aware of these issues before planting them.

Here are some of the most common problems with cherry laurels in the landscape and what you can do.

Disease

• Cherry shot hole disease – The leaves have a shot hole pattern that looks like it was caused by an insect. However, this is a foliar fungal disease favored by wet weather. The infected leaf tissue falls out and the holes are left behind. The damage is cosmetic and no chemical controls are recommended. Rake up any fallen foliage. The plant will recover.

  

Insects

• Peachtree borer – Feeding by this insect causes branch dieback and leaf browning. Look around the base of the stems for holes in the bark and frass (sawdust). This borer is attracted to excessive mulch and deep planting. Keep mulch no thicker than 2 inches and away from the base of the stems. When planting, set the shrub slightly higher than the existing soil grade in heavy clay soils. There are no chemical controls.
• White prunicola scale – Feeding by heavy infestations of this insect can cause leaf yellowing and dieback. Look for white scale covers (white stuff) on the trunks and branches. This is an armored scale that sucks out cell contents. It is often found on weakened plants.

  

  Prune out any dead or dying branches. If the infestation is not heavy, use a soft brush to brush away the white scale covers from the branches. During the growing season, wrap a piece of double-sided tape around one of the branches. This is a test to monitor the active crawler (juvenile) stage of these insects. They are more susceptible when they come out in May/June depending upon temperature and there may be several generations per year. When you see crawlers sticking to the tape, that is a good time to apply horticultural or insecticidal soap according to label directions.

Abiotic Problems

• Poor drainage – Leaves may show yellowing, browning, and dieback. Cherry laurels do not like a heavy clay soil that drains poorly. Excess soil moisture reduces oxygen in the soil, damages fine root hairs, and the root system is unable to absorb water. Be sure to check the soil drainage and make sure there are no downspouts dumping water in the root zone. Plant in raised beds and/or divert downspouts to another location.
• Winter damage – This shows up as leaf browning and scorch when temperatures warm up in the spring. Broad-leaved evergreens are susceptible to drying winter winds, low temperatures, late frosts or freezes. Water deeply so there is enough moisture available to the roots before the ground freezes.

  

To establish cherry laurels successfully in your landscape, here are tips for new and established plants.

• Check the soil drainage and make sure there are no downspouts dumping water in the site.
• Before planting, if the roots are root-bound within the container, make several cuts along the outside of the root ball and tease the roots out so they can establish into the surrounding soil. (See Planting Process.)
• Do not plant too deeply. Dig the planting hole deep enough to accommodate the plant with the top of the root ball level with or slightly above ground level.
• Mulch should be no thicker than 2-3 inches. Keep it several inches away from the stems of the plants.
• Check the soil moisture of new plants weekly and water deeply. Water established plants during dry periods.

If you notice problems with your shrubs during the growing season, we are happy to help diagnose what you are dealing with. Please send your questions and clear photos to the Home & Garden Information Center’s Ask Extension service.

By Marian Hengemihle, Maryland Certified Professional Horticulturist, Consultant, University of Maryland Extension Home & Garden Information Center

More on this topic: Cherry Laurel: Identify and Manage Problems, from the University of Maryland Extension (February 2024)