Q. My hollies have many yellow leaves, are they diseased? My other plants have similar problems and I wonder what can be done?
A. Spring is in the air and in the soil and plants are responding to signals from nature. Gardeners have to recognize certain traits of their favorite plants.
Evergreen plants do keep the foliage throughout the year but they do shed their older foliage and this process depends very much on the genetic "schedule" of the plant and the weather patterns of their surroundings. Many gardeners get very worried when their pine trees display many yellow needles, then drop lots of them. In general, pines may have a heavy needle drop every other year. You may notice a much thicker layer of pine needles in one year and then a light drop the next.
Your hollies, especially native American hollies, are having a year for heavy leaf drop. You can be more relaxed about any kind of leaf drop on your evergreens if you carefully note which leaves or needles are dropping.
Here's what to look for: Old yellow leaves down the stem and closer to the trunk, then new green growth at the tip of the plant. Older leaves will be large, maybe scarred or damaged and will be clustered together. They are being shed by the tree as it grows outward.
As long as you can see new green growth at the tips, your plant is probably healthy. Look carefully at the new tender growth and inspect it for signs of insect or fungus damage. Most insects are programmed to head for juicy new foliage and they avoid old tough leaves.
So every year, depending on weather patterns -- lots of rain, no rain, late cold, early heat -- all these factors affect plant growth and healthy leaf drop. This is why gardening is so interesting, every year is different. Check carefully and, if you are still worried, cut a small branch and bring it to your favorite plant nursery for diagnosis.
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