| ||||||
A eucalyptus fell on Lafayette Circle, damaging several cars in the La Finestra parking lot and blocking the roadway, while a Valley Oak toppled at the corner of Burton and Lucas Drives, causing extensive damage to one of the homes on a corner lot.
Mike Moran, Director of Public Works for the City of Lafayette, expressed relief that no one was killed. "The issue of falling trees is keeping me up nights," he said.
The popular perception is that the combination of five years of prolonged drought, along with the recent above-average rainfall, led to the trees' demise. However, many other factors contribute to the danger posed by falling trees.
"Many of the homes in Lafayette were built 60-70 years ago," said Moran. "The trees were there before and are no longer in the best conditions to grow. Many are now near sidewalks or roadways and, like animal species, have lost their habitat."
Saranap resident John Traverso, owner of Traverso Tree Service and a certified arborist, estimated that the oak tree that fell was an estimated 250 years old and suffered from the street being moved 10 feet closer. In addition, he added, all water going down a crack in the gutter went beneath the tree. Roots had been damaged beneath the upper layer and rotted out.
"From the surface, no one could have seen the damage to the oak, but the eucalyptus was a different matter." said Moran. "It was clearly overgrown and prime for a fall."
Public Works Director Edric Kwan of Moraga says that the town has been pretty lucky so far, but there was a big tree that fell on Augusta Drive near the Country Club.
"Homeowners should be aware that they are responsible for the trees around their property," warned Kwan. "Public Works will remove a tree that is blocking a roadway, but the property owner will have to pay for that service." He added that the homeowner's insurance usually covers the cost.
Precautions for Homeowners
Moran also cautions that property owners are responsible for the maintenance of trees adjacent to their property (ie. sidewalk trees).
"Many of the older and bigger eucalyptus and pine trees have problems and are already on the way out," said Moran. "The eucalyptus have shallow foundations and should be pruned regularly, while many pine trees have been decimated by bark beetles."
One large problem with existing trees is too much landscape irrigation. Direct water on tree trunks, growing lawn around trees and over mulching can all compromise a tree. Traverso recommends keeping water at least 10 feet away from the trunk.
Traverso estimates it may take up to three to five years for problems to decrease from the past drought. "One good winter may actually contribute to further failures. Early storms brought down the weaker and smaller trees, while worse storms are bringing down bigger ones."
Traverso also mentioned a large problem for tree owners: summer (or sudden) limb drop in warmer weather. "Throw in 100-degree heat and a drop in the weather at night and it can cause a defect in the branch to break and fall."
Traverso and Moran both suggest that if homeowners have any doubt about the condition of their trees they should consult a qualified arborist for an evaluation. Most companies would evaluate and submit a bid for free. People can also check the www.treesaregood.com website for a qualified tree risk assessor from the International Society of Arboriculture.
Danger of Falling Trees -What to Look For:
Uncorrected Leans: The upright growth of the tree has been compromised. This could happen for a variety of reasons (shade constraints, trauma, etc.). To check if a tree is leaning more, drive two screws into different levels of tree and check with a digitalized level. Measure again periodically to see if there is increased angle.
Fungi: Various fungi can cause damage to the tree's trunk. Most commonly, Armillaria, sometimes called the oak root fungus, can infect the roots. Because of this, detection is difficult unless characteristic mushrooms are produced around the base of the tree or symptoms become obvious in the crown or on the lower stem.
Generally, the foliage thins and discolors, turns yellow, then brown; branches die back; and shoot and foliar growth are reduced.
On large, lightly infected or vigorous trees, crown symptoms develop over a number of years until the trees die. Conifers, particularly Douglas fir and western larch, frequently produce a larger-than-normal crop of cones, known as stress cones, shortly before they die.
On most conifers, the infected portions of the lower stems are somewhat enlarged and exude large amounts of resin. Infected portions of the roots frequently become heavily encrusted with resin, soil and fungal tissue. Other fungi can include brown rot and shelf conks, which resemble seashells protruding from the trunk.
Drought stress: Symptoms are often the same as fungal damage, but without the presence of fungi.
Buried trunk: The trunk resembles a buried telephone pole. This can be the result of overmulching or excessive watering. Digging around the base may reveal root damage.
Root restriction: Factors such as nearby concrete, foundations, retaining walls, pathways, etc., may limit root extension. Girdling roots may be found wrapping around the base of the tree.
Excessive pruning. Improper or excessive pruning can compromise a tree and lead to failure. Over-thinning the interior of the tree (called lions-tailing), unbalances the crown causing future growth toward the ends of remaining branches. This shifts the center of gravity higher where wind speed is greater. Branches may break more easily in storms or under their own weight.
Multiple trunks: Trees with more than one dominate trunk can have a tendency to split, causing major portions of the tree to fall.
Vine growth: Vines can cause structural problems. Added weight can break branches or cause tree to topple. Debris and moisture can be trapped against the trunk leading to fungal and bacterial diseases and structural decay at the base of the tree.
Sources: U.S. Department of Agriculture Forest Service; Urban Tree Foundation; The Britton Fund; Midwestern Trees; John Traverso, Arborist
Reach the reporter at:
Lamorinda Weekly, Moraga CA