What Is It?
The sudden drop of branches and limbs during summer in the absence of apparent damage or defects.
When It Can Happen
- hot summer days with little to no wind
- during dry periods after prolonged wet periods
- during wet periods after prolonged dry periods
Why It Happens
Too Much Weight
After spring growth spurts, trees are weighed down with leaves and fruit. During dry summer months, the wood becomes brittle and breaks from all the weight.
Too Little Water
Lack of water increases internal branch temperature and ethylene hormone concentration. Ethylene weakens the branch, resulting in failure. This can be the tree’s response to stress. It “knows” it can’t support all its branches, so it sheds a branch or two.
Water Uptake After Drought Stress
Sudden water intake after a dry spell weighs down the branch, which was previously weakened during drought. The branch is now more likely to break.
Too Hot & Humid
On hot days, trees absorb lots of water into the leaves. But if it’s humid, the water can’t evaporate out of the leaves, which then weighs down and breaks the branches.
How to Prevent It
- Irrigate properly and regularly.
- Prune off excess end weight, but watch for watersprouts, which will add weight.
- Be extra cautious around mature trees with large horizontal limbs.