We know that stress can cause trees and shrubs to put more energy into seed production. The strategy seems to produce lots of seed in case the “mother” plant dies. This large expenditure of energy means that there was less energy left over to push out leaves in the spring resulting in delayed leaf emergence.
So, let’s look at the likely cause. Remember the flowers and seeds that were produced this year came from buds that were produced last year during the growing season. Therefore, it was a stress that came last year that caused the problem. Actually, I think it was a stress from the Fall of 2017 through much of the Spring of 2018 that triggered the plants. In the Manhattan area, we had adequate rainfall through October of 2017, but then virtually nothing until May of 2018. This drought was severe enough that root systems were likely damaged so that even when rainfall returned, the plant was under moisture stress, especially in the upper portions of the tree. This stress, then, stimulated the plant to set an abnormally high number of fruit buds resulting in tremendous flowering and seed production this year.
What do we do about this? First, don’t assume a tree is dead if leaves don’t appear immediately. Also, don’t assume the top portion of the tree is dead if it is slower to leaf out than the lower portions of the tree. Give the tree a few more weeks and see what happens.
Next, these trees and shrubs don’t have a lot of energy reserves left so they need to be given extra care. Primarily this means watering as needed. Keep in mind that too much water is as bad as too little. Roots need to breathe; they need oxygen. With the excessive rains much of Kansas has received recently, it may be a while before watering needs to be done. Just don’t wait too long as the damaged root system will not be as efficient in taking up the water the plant needs. So when do you start watering? Use a screwdriver to try to penetrate the soil under the tree. If it is difficult to push the tang of the screwdriver into the soil, it is time to water. Water enough so that the soil is moist to a depth of one foot. Use a long-tanged screwdriver, a wooden dowel or a metal rod such as a section of rebar or electric fence post to test. It will stop when it hits dry soil. (Ward Upham)