Pine trees are not native to Portola Valley, Woodside and the Woodside Fire Protection District in general, and large numbers of them are suffering from the drought.
"Overwhelmingly, pine trees have been hit the hardest," said fire district Fire Marshal Denise Enea. "Some of our pines were already infested with bark beetle and the drought has compounded the health issue. ... We are seeing hundreds of pines die within the fire district."
Pines are native to the Monterey Peninsula, said arborist Kevin Kielty. In addition to the drought, their decline can be attributed to pine-pitch canker and bark beetle, he said.
Oak debris in parks and open spaces is largely an aftereffect of sudden oak death syndrome, Ms. Enea said.
The fire district is working with Pacific Gas & Electric Co. to remove trees on public land that endanger power lines. Such trees on private property are the responsibility of property owners, who should hire a contractor certified to work near power lines, Ms. Enea said.
Any dead tree that endangers a structure, road, power line or public trail should come down, she added.
Native trees appear to be faring better. At the Portola Valley Town Center, for example, the oaks and redwoods are not showing sign of stress yet, said Public Works Director Howard Young. They must be finding water on their own. "We don't water trees," Mr. Young said.
The town's right-of-way is home to stressed trees, and 90 percent of them are pines, he said. If a tree dies, it will be taken down, he said.
Caring for trees
Trees in need of supplemental irrigation are good candidates for grey water -- recycled water from showers, bathtubs and washing machines, Ms. Enea said.
Trees most in need may be located where concrete restricts where their roots grow, for example, next to a house or driveway or in a median. Also vulnerable are trees with roots injured by construction work, she said.
A layer of mulch at least 4 inches thick around the base of the tree will conserve moisture, she said. Good mulching materials include wood chips, shredded bark, leaves and evergreen needles.
Fertilizers are not appropriate, she said, as they contain damaging salts and could stimulate leaf growth, which would increase moisture loss.
Other stress factors making the drought worse for a tree include construction work nearby, dead and weakened limbs, untreated diseases, and lawn-oriented herbicides in the vicinity, she said.