Volume XXIX Number 1 Page 21

By Gary L. Wade
University of Georgia

Stress in our own lives weakens us and makes us more susceptible to illness. And when environmental problems stress plants, they become vulnerable to diseases and pests.

We can walk away from our stress or can take medicine to relieve it. Plants, though, have to cope until someone changes their environment or moves them to a better place.

To manage stress in the landscape, pay close attention to the site. Select plants that are adapted to it. Change it to better satisfy the plants' requirements. Or apply cultural practices that reduce stress.

Look beyond symptoms

Solve problems by recognizing that the symptoms you see may be secondary. That insect or disease damage, leaf scorching or nutrient deficiency is likely caused by other stresses.

For instance, your azaleas are in an extremely alkaline soil, and you spray them with liquid iron to correct an iron deficiency symptom. It's a short-term solution to a long-term problem.

A good long-term solution? Remove the azaleas to a better site and plant something that's more tolerant of high soil pH. Or remove the alkaline soil and replace it with acidic soil. Or apply acid-forming fertilizers.

Control what you can

We can't control stresses such as ice storms, freezes, floods or drought. But we can help prevent them from damaging plants. First consider the weather catastrophes most likely to happen. Then put sensitive plants where they're less prone to injury.

For instance, put the plants sensitive to moisture stress on raised beds. Place drought-prone plants at lower sites to take advantage of natural drainage.

Some plants such as Heller holly and dwarf Japanese garden juniper can't tolerate extreme fluctuations in soil moisture. They'll be stressed if the soil goes back and forth from very wet to very dry.

Careful placement

Severe winter freezes typically blow from the northwest to the southeast. So put plants that are sensitive to the cold on the south and southeast side of a building or windbreak. That will shelter them from Arctic blasts.

Afternoon shade is critical, too, to ornamentals such as azaleas, dogwoods, redbuds and hydrangeas. Put them on the east side of a building or other source of shade from afternoon sun.

The No. 1 environmental stress in Georgia landscapes is poor soil drainage. The roots of plants growing in wet soils or soils with a high water table literally suffocate and die.

Wet feet

Often just enough roots to sustain the plant will grow just beneath the surface to get much-needed oxygen. A short time of drought, a mild freeze or even fertilizing the plant can damage the remaining surface roots and kill the plants.

A simple perk test will help avoid wet-feet stress. Just dig a hole 2 to 3 feet deep in the native soil and fill it with water.

If more than one-third of the water is still in the hole after 24 hours, improve the drainage before you plant. You can subsoil to break up a hardpan layer, plant on a 12- to 24-inch raised bed or put in drainage pipe.

The right plant

Another excellent way to avoid long-term stress is just to choose the right plant for the site. You don't have to be a walking encyclopedia of plants. But you do need a good reference book.

One good one is "The National Arboretum Book of Outstanding Garden Plants," by Jacqueline Heriteau. It lists plants adapted to a range of sites.

When you select plants, though, never decide on one criterion alone. Red-tip Photinia, for instance, is exceptionally drought-tolerant. But it's extremely susceptible to a leaf spot disease that defoliates it in stressful situations.

A healthy plant is a happy plant. They may not have emotions as we do, but plants waste no time showing us they're stressed. It's our job to remedy these stresses so the plants can thrive.

(Gary Wade is an Extension Service horticulturist with the University of Georgia College of Agricultural and Environmental Sciences.)