Joe’s Journal, Spring Edition: When Weather Goes Wrong – Winter Cold Injury & Spring Frost Damage

Woody plants have evolved structures in order to survive adverse weather conditions. In temperate regions, mechanisms were needed to survive the cold.  In tropical regions, mechanisms were needed to survive seasonal drought. For example, woody deciduous plants form dormant buds that can be either scaly, hairy, viscous, or sticky. Evergreens have modified foliage that are thin or waxy to reduce moisture loss. Evergreens exposed to cold winter winds resist desiccation, but not always. New plantings have a limited root run that increases their susceptibility to wintry weather. The damage is not always immediately visible, but appear in early spring.

Cold weather damage doesn’t stop there.  Following bud break, emerging flowers and foliage are susceptible to spring frosts.

Saucer magnolia with floral necrosis after a cold snap of 25 degrees Fahrenheit
Saucer magnolia with floral necrosis after a cold snap of 25 degrees Fahrenheit

What to Do

In the case of dieback due to low winter temperatures and desiccation, remove the desiccated portions of the plant. Keep the plant mulched, and water during periods of drought.

In the case of spring frost, if only the flowers were killed, as with saucer magnolia, there is little to do.  If on the other hand, foliage was killed, prune back to a yet dormant bud. Select an exterior rather than interior bud, if you have the option.

In either case, avoid high nitrogen fertilization in summer, which will result in succulent tissues that are prone to winter injury or delay the maturation of the dormant buds. Rather, focus on fall applications once leaves turn, and in early spring.  These two seasonal windows are times when trees produce roots.  Select fertilizers that are formulated with at least 50% slow-release nitrogen.

Join me next week when we discuss planting shrubs for spring.

~ Signing off for now, Joe