By Josh Fuder
The drought conditions of the summer and fall have had a big impact on our plants and landscapes. Lawns are crispy and trees went into early dormancy.
Here in Cherokee County, I have two pear trees that went into drought dormancy and just started blossoming a couple of weeks ago. These are all signs that our plants are not getting the water and nutrients they need to grow and store reserves for next year.
Drought is defined by the “absence of rainfall or supplemental moisture for a period of time sufficient to deplete soil moisture and injure plants.” Drought stress results when water loss from the plant exceeds the roots’ ability to absorb water and when the plant’s water content is reduced to the point of interfering with plant processes.
Water is critical for transpiration, which is how the plant moves dissolved nutrients from the roots to the rest of the plant. Without these available nutrients and water, photosynthesis begins to slow or stop.
Woody plants exhibit short-term and long-term responses to drought. Short-term symptoms include wilting, browning of leaves and leaf drop to preserve energy. Long-term symptoms may include twig or branch dieback, reduction in leaf size and decline in flower and fruit production. Severe, long-term symptoms are death, which can occur years after a drought.
During a growing season, plants use their energy for a variety of functions like growth, reproduction and protection. When plant resources are limited, a plant must conserve its energy, so it often favors growth and reproduction. This means that things like walling off injuries from pruning, cankers and insects will often go undone. Without these natural protective measures, disease may manifest a year or two after the drought stress when rainfall has returned to normal levels.
Just because those trees or shrubs drop their leaves and go dormant does not mean we don’t have to worry about them until next spring. It is critical to remember that they will continue to need supplemental moisture during the winter if precipitation does not return to normal levels. Deciduous trees and shrubs will continue to require soil moisture even when the green top growth has ceased for the year.
Follow these recommendations from University of Georgia Cooperative Extension this fall and winter to ensure your plants survive the drought and begin growing again next spring.
Mulch matters: Mulch helps retain soil moisture, regulates soil temperature, controls weeds and adds aesthetic value and organic matter to the soil as it decomposes. Keep a 4-inch layer of mulch around shrubs and out to the drip line of trees.
When to water: The main goal of supplemental watering is to wet the soil several inches deep. Watering a little bit every day or even every few days provides little benefit. This type of watering may actually make your plants more prone to drought stress or death because it conditions them to develop shallow, superficial roots. It is better to provide water deeply and infrequently.
Watering at the soil level through drip irrigation or soaker hoses is recommended. This will help reduce leaf and stem wetness, which can cause fungal disease problems. If soils are hard or compacted, soak, wait, then soak again to avoid water runoff. Provide water once a month for mature trees and shrubs or twice monthly for newly established plants.
How much water: Provide 10 gallons per inch of trunk diameter at knee height for trees dispersed across the drip line. For small shrubs (less than 3 feet), apply 5 gallons, and 18 gallons for large shrubs (more than 6 feet). Make sure to put the water where the plants need it most - spread across the drip line.