|We have a massive black walnut tree. We love it, but it is a nuisance. It is the last tree to get leaves in the spring, and the first to drop them in the fall. This year, it started dropping yellow leaves, starting about two weeks ago. It has been dry here (upstate NY) is this causing the earlier than usual drop, or could it be something else? Should it be fertilized? Watered?
Walnut trees normally do leaf out very late in the spring; some old-time gardeners use them as an indicator that spring is truly here.
Leaf drop is a common method for trees to deal with late summer water and/or heat stress. This often happens with black walnut trees in late summer, along with web worm attacks. Since the leaves have already done most of their job for the growing season, it's not usually something to be unduly concerned about unless the tree is defoliating rapidly overall. A certain amount of "tree litter" is normal for these trees throughout the season.
A large established tree should be fine unless under severe drought conditions, or if stressed by some other factor such as root loss due to construction. (If the tree has experienced a stress such as these in the past few years, you might wish to call in a professional arborist for an on-site inspection).