Shade Trees Dropping Leaves
Q: Our shade trees look gorgeous this year due to all the rain. The lindens and burr oak have unusually large, odd-shaped leaves. During the really hot days in July, the trees dropped a lot of leaves so I started watering them. Though the ground was soggy elsewhere, it was surprisingly dry beneath the bigger trees. Watering seemed to help and then the rains started again. They are dropping a lot less foliage now. Should I water them even if it rains?
A: Hello fellow soggy gardener! I too noticed this phenomenon with my elms. It’s very dry underneath bigger, older trees. Their canopies shed rain to the the dripline like an umbrella. I can’t think of a reason for this except that perhaps in their native habitats trees shed away excessive moisture to protect their roots from rot. Of course, this is generally not the case here.
Since trees produced so much extra canopy this year, it’s possible they exhausted their food reserves. Plants reallocate carbohydrates from older to newer leaves if food is lacking and could be why the plants are “dumping” older, less efficient leaf “factories”. So yes, continue watering if the soil beneath the canopy is dry.
Because tree roots in our area tend to be quite shallow (less than a foot deep) surface applications of organic fertilizers like composted manure, alfalfa-based, or even dried poultry waste fertilizers really help with the tree’s overall vigor and longevity.