Q. My evergreen oak tree is over 20 years old. Some of the leaves are turning yellow and dropping while there is some new growth, but not as vigorous as prior years. It is on drip and gets a deep watering twice a month. There is five-foot circle underneath with no rock. It also was deep root fertilized in February by a commercial company.
|Yellow leaf drop can be normal on evergreen trees|
A. If the yellowing and leaf drop is from older growth and not excessive it is probably normal. Evergreen trees like southern live or holly oak display leaf drop starting in the spring at the same time as new growth.
As new growth develops, older leaves begin to drop. All evergreen trees, including pine trees, show leaf or needle drop of the older ones and retain the younger ones until they also become too old and drop.
|Pine needle drop can be normal as it drops older needles as new ones develop|
The tree wants its young growth in the sun since it is more efficient at gathering light. The older growth is in the shade and is less efficient at gathering light. Leaves growing in the shade can be a detriment to the tree. They may consume more than they produce.
It is in the tree’s best interest to drop older leaves. If leaf drop is occurring on new growth then I would be more concerned.
On another note, as trees get larger they require more water. A sign the tree is not getting enough water is a lack of vigorous growth. You might consider adding more drip emitters to the tree so that it waters a larger area if you believe it is not getting enough water.