How to determine if your trees and shrubs can bounce back after stressful summer

Sunday, October 14, 2012
Paul Schnare shows the effects of heat stress on a deciduous tree. (Laura Simon)

Over the last few weeks I have looked at trees and shrubs that exhibit damage resulting from the stressful summer. Samples of stressed plants are brought to me every day to look at, and telephone callers describe damage that they see on the plants in their landscape.

After the introductory examination or description of the damage, the gardener's inevitable question is, "Should I cut them down now and replace them, or should I fertilize them and wait and see what happens next spring?"

The answer to the question depends upon many factors including how much money you are willing to spend, and how patient you are.

If your tree or shrub is an evergreen that exhibits more than 50 percent brown foliage, bend the twigs where the foliage is brown. If the twig snaps, that branch is probably dead. If it bends then the branch is green and may survive and produce leaves or needles next spring.

If you are patient, you may want to see how the evergreen plant grows next spring. It could possibly fill in over a season or two and do quite well from then on.

Paul Schnare shows the effects of heat stress on an evergreen bush. (Laura Simon)

If you wait until next spring to decide whether or not to keep the plant in your landscape, you should fertilize it this fall with bone meal or super phosphate to encourage any root growth. Don't use a fertilizer with a lot of nitrogen in it at this time of the year because nitrogen will encourage the plant to continue growing instead of slowly going into dormancy.

I would also suggest that you spray both damaged and undamaged broadleaf evergreens, such as boxwood, azalea, holly and nandina with Anti-Stress 2000. This product plugs up the pores of the leaves so no moisture will be lost through the leaves during the winter. This application will prevent or reduce the possibility of winter burn, another form of plant stress.

If your evergreen shrub has 50 percent or more brown foliage, and it is situated in a very prominent place in your landscape, you may want to go ahead and replace it this fall. Christmas decorations on a brown shrub may put a damper on the holidays.

A brown deciduous shrub or tree requires a little more investigating. First, bend twigs to determine if they snap or bend. You may also want to scrape the bark of larger branches with your fingernail. If you find green at the scrape, the branch is still alive.

I would probably wait until next spring to decide whether to replace a deciduous tree or shrub. I have seen "dead Japanese maples" regrow branches to the point that they actually look better than before they experienced the environmental stress period.

Paul Schnare shows the effects of heat stress on a deciduous shrub. (Laura Simon)

If you decide to see how your stressed evergreen and or deciduous trees and shrubs do next year, make sure that you fertilize them early next spring. Use a 19-8-10 with micronutrients. This combination will encourage both root and top growth.

As you watch the growth of your stressed landscape plants next spring you can replace them if need be. You will have plenty of time to rip out the old plant and put in a new one before the stress of summer comes on.

P.S. I have fielded several calls about spring blooming plants such as azaleas, lilacs, quince and pear that are blooming in the fall. Many gardeners have never seen this happen and are concerned that the plants, blooming out of season, are getting ready to die.

I have seen this quite often. After a stressful summer, these plants flower in order to ensure that if stress does continue, their species will survive. Don't worry. Very seldom have I seen a spring blooming plant that blooms in the fall not do well the next growing season. It may not bloom next spring, but it will survive.

Send your gardening and landscape questions to Paul Schnare at P.O. Box 699, Cape Girardeau, MO 63702-0699 or by email to news@semissourian.com.

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