Why is my cottonwood dropping branches in summer?

What sudden limb drop is

A city arborist's note from Menlo Park, California describes it as an otherwise healthy-looking branch that breaks unexpectedly, mostly on mature trees with long horizontal limbs that carry a great deal of weight at their tips. It gives several explanations: high heat can dry and shrink internal wood and cause microscopic cracks, and on hot, calm days a tree can take in water faster than the leaves release it, adding weight to a branch.

These are explanations offered for the pattern, not a settled cause, and the note is from California, not Nevada. We use it for the idea, not the details.

Why cottonwoods get the worry

Fremont cottonwoods grow fast and wide along Northern Nevada streams and ditches, and an old one can carry heavy limbs over a yard, a fence or a driveway. Our Fremont cottonwood page covers its habits, and the guide on cottonwoods: keep, prune or remove covers the decision.

A branch that has dropped once is a reason to look at the rest, because a second one may come. Decay at the break is also worth seeing; see root and trunk decay.

What an arborist does

The arborist looks at the limb attachments, any cracks, dead wood and the crown shape, and says whether the answer is dead wooding, end-weight reduction, cabling or removal of a limb or the tree. The Menlo Park note also recommends deep watering in heat waves, proper mulching and routine inspections by a certified arborist.

We never tell anyone from a description that a tree is safe. Keep people, cars and seating out from under big limbs on hot afternoons, and if a limb hangs over a line, call NV Energy. Our two ISA Certified Arborists give free estimates: 775.232.8243.