One of Life’s Mysteries, Summer Branch Drop

It’s common to look for broken or damaged tree limbs after a storm. However, don’t get lulled into thinking that’s the only time you’ll find branches in your yard.

On windless high 80- and 90-digit degree days, branches can suddenly fall in your neighborhood. What causes it?  Too much heat? Too little water? Another aftermath of drought?

Why does sudden branch drop occur? There really isn’t one answer to this question, according to Ned Patchett Consulting. That’s because it affects both trees in watered landscapes and native trees that aren’t irrigated.

Quite simply, it’s a common syndrome when trees struggle to balance the water coming in and leaving via transpiration. Transpiration is how trees take up water through their roots, and then give off water vapor (or moisture) through pores in leaves. This is due to high humidity in tree canopies on hot days, which can result in higher pressure and moisture content inside the branch, making it heavier.

Keep an eye on your trees – older trees in particular. Older oak, maple, ash, beech and elm trees are susceptible to sudden branch drop. But it also occurs in other species including sycamore, cypress, liquidambar, Eucalyptus and ash trees.

The phenomenon has been called “summer branch drop,” “summer limb drop” and “sudden branch drop” syndrome, according to the horticulture department at the University of California Davis Arboretum. It tends to occur during really high temperatures. A loud crack is often heard before the limb falls to the ground.

According to research from the University of California Cooperative Extension Service, summer branch drop most likely happens in the afternoon on hot, calm days. How the branch breaks is different, too. Instead of snapping off near the trunk – as it does with wind-related breaks – large diameter limbs will break three to 12 feet from the trunk.

Upright branches are rarely susceptible to sudden limb drop; however, watch out for long branches that run parallel to the ground, and stretch out past the edges of the tree’s canopy or, the outer fringe of its foliage. Those are the most likely to drop.

Additionally, a tree that has dropped one branch in summer is more likely to drop another during its lifetime.

What happens exactly? On a hot day, trees soak up more water from the ground faster than it can release the moisture into the air. As a result, limbs become too heavy, break and fall to the ground.

Most common, a true summer limb drop breaks about three feet from the tree trunk. Limbs that fit the profile for sudden drop syndrome are limbs that are:

  • Mature
  • Large
  • Horizontal
  • Extending beyond the main canopy of the tree

To reduce the risk, Ned Patchett Consulting suggests tree owners should take these four preventive measures:

  • Consult an arborist to identify if your tree is at risk for summer branch drop.
  • Hire an arborist who can perform quality pruning which avoids flush cuts, excessive thinning and Lion’s-tailing.
  • Timely tree health care including fertilization and insect, disease prevention and control.
  • Appropriate watering practices.

Proper watering can be the biggest challenge. Why?

  • Improper watering – generally overwatering – is common.
  • Light, frequent watering over a long period of time weakens trees. This promotes shallow, week root systems.
  • It’s best to water less often for longer durations to promote deep healthy root systems

Other causes of summer tree branch drop can include:

  • Tissue shrinkage due to heat.
  • Internal cracks in the branches.
  • Deterioration in cell wall structure of the tree potential caused by gas released in the tissue caused by wet wood bacteria.

Ultimately, when it gets too hot, the tree responds by letting a limb go; also known as auto-amputation.

When inspecting your trees, look for discoloration, or a darker spot where water appears to be bleeding out of the tree. This is a sign of a potential limb flaw.

Pay attention to your trees, work with a tree care professional and don’t park vehicles under a big tree on a hot day, calm days and evenings.

Are you looking for an innovative tree service and landscape design and maintenance company that will uniquely and passionately create and care for your trees and yard like they were their own?

Let the experienced professionals at Ned Patchett Consulting deliver for you. Connect with us at or 650-728-8308

#nedpatchettconsulting #suddenlimbdrop #treehealth #arborist #treecareprofessional

By |2020-01-20T21:41:01+00:00September 2nd, 2018|Blog|