Published in the Contra Costa Times on August 19, 2006

Q. I came home to find a large limb from my mature Liquidamber tree on the front lawn. There is no sign of disease or insect damage. Do I need to take the tree out?

A. Large healthy tree can lose limbs abruptly and without warning in the heat of the summer. The cause of ‘Summer Limb Drop’ in not well understood, but it is recognized as a real problem. The ‘California tree Failure Report Program’ has been collecting data on the species that appear to be most susceptible, and Liquidamber tops the list. July is the most common month for limb drop, with most failures occurring in the afternoon on days with little to no wind.

Taking out the tree is not necessary unless you are concerned about liability. The limbs that fail are usually long horizontal branches. These branches should be shortened or removed. The branches can be thinned to lighten the weight, or pruned back to an upright shoot closer to the trunk. The UC recommendations for general tree health include the following:

• Prune trees to encourage tapered branches
• Maintain tree health and encourage only moderate growth.
• Inspect trees regularly for cracking, signs on decay of development of cavities.
• Remove damaged limbs promptly
• Trees that are in decline should be removed, or activity beneath them should be restricted.
• Avoid planting species susceptible to summer limb failure in areas that are frequently used: liquidamber, eucalyptus, oak, ash, ornamental pear, sycamore, silver maple and poplar.

Having your tree inspected by a consulting arborist will give you the best information on how to approach your specific situation. You can find the phone numbers and email for local consulting arborists on the International Society of Arborists website: http://www.isa-arbor.com/