An inspection of oak trees at Rinconada Park in Palo Alto after a large tree fell onto Walter Hays Elementary School grounds last month has found one more tree that must be removed, City of Palo Alto's urban forester said.
The city conducted root inspections of similar oaks as the one that fell on Jan. 4 and discovered the roots of another coast live oak on Embarcadero Road were compromised, Urban Forester Walter Passmore said in a statement. City crews are scheduled to remove the tree on or after Feb.22. Replacement trees will be planted in March.
Crews inspected the trees by excavating and temporarily removing soil to assess below-ground root conditions. The majority of the root systems of the park's large coast live oaks are in fair to good condition. The Rinconada Oak, a designated heritage tree, has a healthy root system and is likely to live for many more years, inspectors found.
One oak, however, is in poor condition, poses a safety hazard and must be removed. The tree has severe root decay that has rotted 40 percent of the exterior of the base of the trunk and compromised large anchor roots. The tree is the nearest neighbor to the one that fell in January.
Tree decline is often caused by an accumulation of stressors, Passmore said. Old age reduces a tree's tolerance to changing conditions and reduces resilience to insects and disease. The root rot on the tree outpaced the tree's ability to grow new roots, which has reduced the ability of the roots to anchor the tree to the soil, he said.
"Trees are living organisms with a finite life span, and after careful consideration of the inspection results, we recommend that this tree be removed due to advanced decay in the root system. This tree has a high risk of failure due its condition and no treatment is available that will allow new growth to outpace the decay," Passmore said in a statement.
City crews will recycle the tree, and the wood will be used as mulch to sustain other trees, he said. A planting plan has been developed to replace the fallen tree and the tree proposed for removal.
Passmore said the goal is to plant more than 10 large-growing oak trees with compatible shade-tolerant smaller trees in the next two months. New trees can be established this planting season prior to mid-March, he said. Many of the established trees in the park will receive maintenance pruning and mulching to improve their health and safety, he added.