Question: My trees are dropping lots of their leaves prematurely. What could be causing that? They’re turning yellow before they drop.
Answer: Generally that’s a symptom of moisture stress, and usually it’s because the leaves haven’t gotten the water they need. It can be from dry soils, of course, but it can also be caused by damage to the roots or trunk. It’s a very common problem with large-leafed, fast-growing trees such as sycamores, fruitless mulberries, cottonwoods, silver maples, catalpas and varnish trees, among others. Those trees put out large numbers of leaves in cool, moist spring weather, only to run into the “wall” of heat by mid-July. Let the hose run slowly beneath them to supplement the water you give your turf, but be prepared to see a certain amount of the leaf drop anyway.