April 13, 2007 | By: Carol Lea Spence
LEXINGTON, KY.

Across the state, the recent freeze came on the heels of an unseasonably warm March, so when the arctic blast hit, woody plants were bursting with lush, new growth, and many perennials had broken dormancy earlier than usual. The four-day stretch of frigid air did substantial damage because plants were at their most vulnerable stage.

“I have not observed anything like this in my 29 years in west Kentucky,” said Winston Dunwell, University of Kentucky Cooperative Extension nursery crop specialist. “The damage is extensive.”

When faced with what appears to be a home landscape decimated by a hundred-year weather event, it’s easy for the home gardener to panic. The word from extension specialists is: Don’t.

“The best advice is to do nothing at this point in time,” said Bill Fountain, UK extension arboriculture specialist. “Plants have adapted to adversity with multiple secondary methods for remaining alive. Remember, Mother Nature never said that plants had to be as perfect in form and habit as people would like for them to be.”

“We are watching and waiting to see if the damage will be limited to flowers (and ultimately ornamental fruit loss), leaves and new tender stem growth, or if there will be bark damage and how extensive will it be,” Dunwell said.

Rick Durham, UK extension consumer horticulture specialist holds out hope.

“My take is that even though things look pretty well gone, most will put out a second growth flush in a few weeks,” he said. “This would include herbaceous perennials and most woody plants.”

According to Fountain, whether a plant recovers depends on a number of things: the stage of the plant at the time of the freeze, what the low temperature was, how long it stayed below freezing, how quickly it gets hot again (the slower the better), the age and health of the plant, and the species and cultivar. His advice? Don’t fret. Worry will not help the plant.

A plant’s goal in life, Fountain said, is to reproduce as much as it can before it dies, so it has backup buds in reserve in case the terminal shoots are killed. He recommends giving woody plants time to recover and sprout again.

Dunwell agreed. 

“Woody ornamental plants frequently surprise us with their resiliency, making for an optimistic outlook,” he said.

When examining trees and shrubs for damage, look first at the leaves.

“If the leaves look like corn flakes, they’re dead, don’t worry about them, they’re going to fall off,” said Fountain, adding, “Don’t pick these dead leaves off. Doing so might damage buds that are still alive at the base of the dead foliage. Just let these dead leaves fall off naturally.”

Examine the base of the leaves to find last year’s buds. Open up the bud with your fingernail. If it’s dry, then the bud is dead, and Fountain says regrowth at that point will be very poor. Take a knife and slice into the stem. If you see purpling showing up just below the bark, that’s an indication that you have extreme damage. Be aware, however, that this does not apply to trees and shrubs with purple foliage. They will naturally show purple below the bark.

Once new growth does appear and you have ascertained which branches are dead, it’s safe to go in and do judicious pruning, Fountain said. First, remove dead twigs and branches. Then trim areas where multiple shoots have appeared, leaving only the strongest to grow. This is important for trees such as maples, ash, dogwood and buckeye, which have opposite branching. Though the stress of multiple branches fighting for dominance won’t appear immediately, it can often lead to failure in a decade or so.

It might sound like a good idea to help things along with a little fertilizer, but Fountain is adamant about resisting the urge.

“Do not – repeat not – fertilize trees and shrubs,” he said.

Adding nitrogen changes starches within the plant to sugars, which results in rapid shoot growth. It’s healthier for the plant to begin growing slowly and to replace damaged tissues before putting out new growth that will demand water during the typically hot and dry months of summer. 

He suggests watering trees and shrubs during dry spells this summer, to prevent additional stress on the plant. Don’t fertilize until fall and then only if it’s necessary. Use 1 to 2 pounds of slow release or water insoluble nitrogen per 1,000 square feet. The cambium, a layer of cells under the bark that is instrumental in creating a plant’s vascular system, was very active in many shrubs and trees when the freeze hit. Because of that, vertical cracks in trunks may start to appear in May or early June. Fountain said there is nothing that could have been done or can be done at this point to prevent damage. 

“Wrapping the trunk, using duct tape, painting the wound, and nailing or using glue to keep the bark from peeling off is not going to help,” he said. “Some of these trees are going to die, others will be disfigured.”

Many plants will be more susceptible to attack by wood-boring insects. Fountain recommends preventing these attacks rather than trying to kill the insects after damage has already occurred. Check with a certified arborist in your area for more information about preventive methods. A list of International Society of Arboriculture Certified Arborists is available at http://www.isa-arbor.com.

Newly awakened perennials also might have suffered damage. Durham recommends a wait-and-see approach before you decide to dig them up and throw them on the compost pile.

Daylilies and hostas are two common landscape perennials that were in a vigorous growth spurt when the freeze hit and consequently show considerable damage. But Durham said, while the foliage above ground looks pitiful, the plants’ underground growth buds were protected. Now that the foliage has stopped growing, the underground buds will begin the cycle again. In a few weeks, gardeners should see a second flush of growth appear.

“My general recommendation would be to wait a few weeks to see if and where regrowth is occurring and cut back dead tissues at that time,” he said.

“I wish I had some magic words and cures to give you, but ‘wait and see’ is the best advice we can give,” Fountain said. 

For more information about freeze damage or protecting woody plants from insects and disease, contact your local Cooperative Extension office.

Contact: 

William Fountain, 859-257-3320, Rick Durham, 859 257-3249, Winston Dunwell, 270-365-7541