Hi Angie,

There's a good possibility that it is related to the weather, but even though summer branch drop or summer limb failure has long been known to occur, tree experts still have not reached a concensus on exactly why it occurs.

One school of thought is that it is the high flow of moisture through the limb that weakens it....not necessarily a lack of moisture. Rather than resulting from a lack of moisture, it results from all the work the tree's vascular system does to transport enough water throughout the tree to equal the amount of moisture lost to transpiration. Another possible cause is that prior root damage from years before may ultimately lead to summer branch failure, or that it is related to cellulose tissue problems within the limb.

Summer branch failure is most common on large, strongly horizontal limbs, but has been observed on vertical limbs as well. It is observed on some types of trees more than others. A few of the trees we have here in Oklahoma that exhibit summer branch failure more than others include oaks, sycamores, maples and ornamental pears.

There's really nothing you can do about it. It is just one of those things that sometimes happen.

Dawn