The Summer Shed: Understanding Cladoptosis in Trees
Courtney DeKalb-Myers, Assistant Extension Specialist in Consumer Horticulture
July 2026
As conditions transition from the rainy spring into the hot, dry summer, homeowners may notice large trees beginning to drop leaves or small twigs. In most cases, this is a naturally occurring process called cladoptosis. The tree produced more growth than it can support during the spring and is now shedding some of that excess foliage. This helps conserve resources and reduce water loss during the hot, dry periods of summer. This is a beneficial process that helps reduce stress during less-than-ideal conditions. Cladoptosis is common in baldcypress, sycamores, oaks, and some elm species.
Signs of normal cladoptosis include dropped leaves and small twigs, often no bigger than a pencil. The fallen twigs often still have green, healthy-looking leaves attached. Twigs will also have a smooth point of detachment from the tree, rather than appearing broken. This is where an abscission layer formed, allowing the twig to separate. Otherwise, the canopy will generally look healthy.
Although cladoptosis is a normal response to changing environmental conditions, it can be confused with several other issues. Drought stress in trees will also result in dropped leaves, but they will typically appear scorched or wilted. There will also be larger portions of the canopy that appear thin. Heavy winds and storms can also result in fallen twigs and branches, but they lack the clean detachment scar that occurs with cladoptosis. Breaks caused by weather events are often ragged or splintered. Some canker diseases can also cause branch dieback and leaf drop. However, these problems are often accompanied by discolored bark or cracking in major branches. Further investigation may be warranted if larger limbs are falling, the canopy becomes noticeably thin, or the problem persists over multiple years.
Proper care helps trees remain healthy and better tolerate environmental stress. During drought episodes, ensure that trees are watered deeply and infrequently. Water should moisten the soil to a depth of at least 12 inches to allow for maximum water uptake. A small hole can be dug after watering to verify that moisture has reached an adequate depth. Mulch is also important for maintaining soil moisture. Maintain a 2- to 3-inch layer of organic mulch around the tree but keep mulch several inches away from the trunk to reduce the risk of decay. Avoid any unnecessary pruning and heavy fertilizer applications.
Remember that not every fallen leaf or branch indicates a sick tree. In many cases, cladoptosis is the normal process of shedding excess growth and adapting to changing environmental conditions. Knowing the difference between normal self-pruning and signs of decline can help avoid unnecessary concern while recognizing when a tree truly needs attention.
