Harsh winters damage holly, boxwood

Q. What is wrong with my holly and boxwood? I’ve had several sections die out this spring. Could the boxwood have blight?

Lynn from Youngstown

A. We sent a sample of Lynn’s boxwood to the OSU clinic in Columbus to see if boxwood blight was the issue. The sample came back negative.

This is severe winter damage due to not one, but two severe winters in a row. The damage to certain plants seems so severe that it makes many homeowners think there’s a bad disease causing the issues. It is not.

Winter injury (desiccation) happens when the plant cannot take up enough water to replace the water lost by the foliage. Winter desiccation is more severe from to lack of water available to plants in November/December due to low moisture received in the form of rain. Increased winds and cold temperatures make nearly any evergreen plant. The sometimes minimal damage is unnoticed, but even this minimal damage can cause stress, which makes plants even more susceptible to winter desiccation the next year. That, in turn, opens the plant to secondary fungal infections.

In general, Lynn’s shrubs probably had winter desiccation after the 2013-14 winter. The damaged wood was then infected by what she calls “secondary” fungi (as reported in the sample sent to Columbus). That infection caused additional stress, and the more severe desiccation after our 2014-15 winter.

The thing to learn from this:

1. Evergreen shrubs need water in fall, which tends to be dry. This year, the shrubs could have been watered in January when the ground was not frozen.

2. Check evergreen shrubs for signs of stress — small branch cracks, losing more leaves than normal, etc. These may be signs of winter desiccation or location issues.

3. Look to the soil. Make sure the site is well suited for evergreens. Check drainage, level of organic matter, salt used in the area. What is the pH? That can change over time when applying certain fertilizers and mulches. An unsuitable pH makes it challenging for the plant to get the proper nutrition.

4. Pruning. Make sure they’re not pruned until after you see new growth. Many can and will survive; they will just take time to rejuvenate and fill in the bare spots. Allow time for good healing.

5. Fertilization. Most shrubs don’t necessarily need to be fertilized. Check your soil test and keep nutrients at the proper levels.

Eric Barrett is OSU Extension educator for agriculture and natural resources in Mahoning County. Call the office hot line at 330-533-5538 to submit your questions. Clinic hours are Mondays and Thursday from 9 a.m. to noon through October.