The current extended and unexpected drought and hot temperatures are putting the plants in a stressful state, and signals the need to water, says Richard Hentschel, Extension Horticulture Educator for the University of Illinois Extension.
Plants manage drought in a variety of ways from not producing fruits or vegetables to a loss of foliage. Plants in stress are more likely to contract diseases and attract damaging insects. Hentschel says that any time there are fruits (squash, cucumber, eggplant) or pods being filled (peas, snap beans), water needs to be uniformly available. Sweet corn requires even moisture from the time flowers (silks) are pollinated through kernel fill.
Any newly planted trees, shrubs or evergreens will need to be watered during dry periods at the base of the plant outward toward the edge of the planting hole. Shrubs will need to be watered for at least two growing seasons, and trees based on trunk diameter. Hentschel said that typically one year of transplant care for every inch of trunk diameter is a good guideline, but individual home landscape situations will need to be considered. All trees and shrubs will show symptoms of drought after extended dry periods and will need to be watered. Drought is easier to see on a shrub than a large shade tree. Plants growing in a southern or western exposure will require more water than a northern or eastern exposure, even though they are already established. Signs that plants are in stress will be curling or a wilted look, a loss of foliage, or leaves turning yellow and then falling. Increase your watering frequency or adjust your irrigation schedule to provide more water. All large established shade and ornamental trees should be watered. Water should be distributed starting several feet from the trunk and extending past the drip line. This is where the majority of the roots are that will absorb the water. This should take several minutes to several hours per tree, depending on tree size and soil type. Hentschel says it is much harder to see if a needle evergreen is in stress. You can assume that if your trees and shrubs need water, so will your evergreens.
When it comes to lawns, there is a choice, keep the lawn actively growing or allow the lawn to go dormant. Actively growing means the lawn will need to be mowed on a regular basis and that the blades are green and healthy looking. Allowing the lawn to go dormant means the lawn will naturally turn a straw color and cease growing and mowing will not be necessary. About half-inch of water a month will be needed to keep the roots and crown hydrated so as weather moderates the grass plant can return to an actively growing state. Once better weather returns or you decide to bring the lawn out of dormancy, it will take about two weeks for that to happen and the lawn again to turn green.
Hentschel is particularly concerned with all the new parkway plantings going in as the result of all the ash trees being replaced. Many of the trees are showing signs of stress now. Homeowners should consider adopting these trees even though they are on their parkways. These are the trees that will be shading yards or cars in years to come.
How long you will have to provide water is a good guess, says Hentschel. The normal dry period is August, and if the drought continues, it could be a long summer.