The weather in recent weeks has been exceptionally dry, and it appears that another drought may be upon us. Lack of rainfall combined with the unseasonably warm temperatures is creating stressful growing conditions for many landscape plants. The key to keeping them healthy is to apply supplemental water properly and at the right time. Many established ornamental plants can go extended periods without water.
More plants die from overwatering than lack of it, even during droughts. For example, junipers can tolerate prolonged dry spells, but they will perish if over watered or if planted in poorly drained soil.
Plants should receive supplemental water at the first signs of moisture stress, which include wilting and developing a pale gray to green coloration. Lawn areas need water if can you walk across the grass and your foot prints are visible. Excessive soil moisture also produces similar symptoms, such as wilting, causing people to apply more water. This increases the severity of the problem. Soils that stay too wet have reduced oxygen levels which cause the roots to suffocate in addition to promoting the development of root rot diseases. To determine if water is needed, use a small shovel to dig a few inches near the root zone. If the soil feels dry and powdery, then an application of water is needed. Well watered soil will stick together when it is pressed into a ball. The soil should be kept evenly moist, not too dry or too wet.
Often the water only wets the upper couple of inches of the soil and does not penetrate deeply into the root zone. This results from applying only enough water to wet the upper layers of the soil. The roots tend to be weak and shallow and that increases the plant's susceptibility to environmental stresses, insect and disease problems. Water thoroughly and long enough to allow it to penetrate deeply into the soil to encourage the development of a deep extensive root system. Use organic mulches, such as pine straw or pine bark, on the surface of the soil to reduce the loss of water through evaporation.
Make sure the water is reaching the intended plant material. Much of the water applied to landscapes is not absorbed by plants and is lost by evaporation or runoff. On lawns, adjust the sprinklers so they are irrigating the grass, not the pavement. Lawns require roughly one inch of water per week. Place a rain gauge outside to measure the amount of water that the sprinklers are emitting. For trees and shrubs, apply water slowly by hand or use a soaker hose instead of sprinklers to direct the water to the base of the plant. Irrigate before noon in order to reduce the water that is lost through evaporation during the heat of the day. This will also allow the leaves to dry out before nightfall, which will prevent the development of diseases.
As the dry spell continues, combined with the possibility of water restrictions, applying water correctly and efficiently will help improve the likelihood of keeping plants in the landscape healthy. It will also help conserve water which is critical during periods of limited rainfall.
Timothy Daly, MS, is an Agricultural and Natural Resource Extension Agent, Gwinnett County Extension.
He can be contacted by phone at 678-377-4010 or by email at firstname.lastname@example.org.