Leaves

Cercospora leaf spot on crepe myrtle may not be recognized as a disease, since affected leaves turn colors like healthy leaves do in early fall. On the top row, round, tan spots are visible on the left and center leaves. A disease-free leaf is shown in the upper right-hand corner. Leaves on the bottom row show various stages of the disease. Provided

After a hurricane has passed, it’s time to examine landscape plants to see what kind of care they need to recover. The following suggestions are not hard-and-fast rules, since, to my knowledge, no one has experimented on hurricane-damaged plants to verify the best practices. These guidelines are (mostly) taken from general plant care.

Clean up

The most important task is removing damaged limbs and branches on woody trees and shrubs. Make a clean cut at the base of the branch where it is attached to the next largest branch. A “clean” cut with a smooth surface allows the branch to heal itself by sealing the cut to keep wood-decaying fungi out.

According to the city of Charleston yard waste regulations, branches must be cut into four-foot lengths for pick up. This ordinance is still in effect after a storm.

I don’t know if the saying “beware of chiggers in Spanish moss” is a rule of thumb, an old wives’ tale or an urban legend, but in 20 years of cleaning up Spanish moss in my yard, I’ve never encountered chiggers. Some say they infest only clumps laying on the ground. Let’s just agree that the risk of contacting chiggers from handling Spanish moss is overblown.

When cleaning up debris, watch for snakes. When we returned from evacuating, a large, curious yellow rat snake “greeted” us at the front door. Snakes may be displaced from holes in fallen trees or from dens in the ground that flooded. Even though rat snakes can be 5 feet long, they are harmless to humans.

If you are an impatient composter like me, don’t put twigs and oak leaves in a compost pile, since they decay slowly. Let a municipal compost facility use them in long windrows that are turned with front-end loaders.

Hurricane debris is a good source of material for a Huegelkultur long-term compost pile in layers with limbs on the bottom, branches with leaves, grass or grass clippings and soil on top. 

Before removing damaged plants, wait three to six months to allow them to attempt to recover. 

Aftercare

Although fertilizer normally is not recommended this late in the growing season, a light dose can help perennial plants recover from leaf loss. Fertilize evergreen shrubs with one-quarter the recommended rate if they were fertilized in the past three months, and use half the rate if fertilized in the past six months or longer. Low nitrogen fertilizer (5-0-10) should be used. Plants that lost only a few leaves do not need fertilizing.

Deciduous shrubs that lose their leaves in the fall should not be fertilized now, but they should be fertilized next spring so they develop a full set of leaves.

Plants, both woody and herbaceous, may need to be staked after a hurricane so that they resume upright growth.

Injury or disease?

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Plants may turn yellow or brown due to injuries or diseases after a hurricane. Injury is the result of physical damage that happens over a limited period.

Rain that comes with a hurricane probably dilutes the saltiness of ocean water enough to prevent widespread injury from saltwater hitting leaves. River birches and red maples, however, have low tolerance to salt spray.

A more serious plant concern is salt-water storm surges. The best defense is to plant salt-tolerant plants in areas at risk from seawater flooding.

Plants that have been sheltered in shady spots during a hurricane should be moved to partly sunny spots for one to two days before returning them to full-sun spots. A gradual readjustment to the intense sunshine that normally follows a hurricane will prevent sunburn and excessive wilting.

Disease is caused by a pathogenic microorganism that attacks plants, often after excess rain. Black rot on fall leafy brassica crops, like collard and kale, often starts after hurricanes. The wind blows sand particles that injure leaves, and it spreads black rot bacteria. 

Once symptoms appear, there is no cure for black rot. Diseased plants should be removed from the garden.

The yellow color appearing on crepe myrtle leaves is Cercospora leaf spot, a disease that flourishes after leaves stayed wet for two days during rain from Hurricane Dorian. Spraying is not effective after symptoms appear, so fallen leaves should be raked and disposed in yard waste.

Anthony Keinath is professor of plant pathology at the Clemson Coastal Research & Education Center in Charleston. His expertise is in diseases of vegetables. He is also an avid gardener. Contact him at tknth@clemson.edu.