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When crushing heat hammers the Bay Area, residents are advised to not only stay hydrated themselves, but give their trees a drink as well.

Temperatures have soared across the region this week, hitting a record-breaking 116 degrees in Livermore on Tuesday and smashing records in King City, Santa Rosa, Napa, Redwood City and San Jose as well. As a result, drought-stressed trees are suffering even more, said arborist Darya Barar of East Bay-based HortScience/Bartlett Consulting.

“Any time there is high heat, trees are water-stressed,” said Barar, whose firm provides tree management services to businesses and municipalities. Trees were already suffering from the drought crisis facing the state, and the recent heat wave added insult to injury, she said.

Trees’ immune systems are more susceptible to pests and disease with less water. Some species, like the coast redwood, have seen an “insanely steep” decline over the last 10 years due to the drought, the arborist said.

The solution: Grab a hose and get to work.

“Eighty percent of sprinkler water runs off. It comes out so quickly, the soil doesn’t have time to absorb the water.”

Darya Barar, arborist

“People often don’t think trees, especially mature trees, need to be irrigated, but that is not the case,” Barar said. She added that while the coast live oak and valley oak don’t need summer watering, they will benefit from watering October through May.

Along those lines, “You can definitely help save trees now by giving them a couple of good deep waterings,” said Stephen Pree, El Cerrito’s city arborist.

“On mature trees, it’s important to water deeply and infrequently,” Pree said. “The water should be trickling slowly out of the hose — just dripping out. Put the hose at the edge of the drip line.” The “drip line” is directly below the leaves on the outermost part of the tree.

Barar of HortScience added that the hose should be left in place for a couple of hours, allowing the water to penetrate the soil. According to Barar, “Eighty percent of sprinkler water runs off. It comes out so quickly, the soil doesn’t have time to absorb the water.”

Barar advises watering twice a week during high heat and periods of no rain, though this may vary depending on the type of soil and other variables. She suggested visiting the Arbor Day Foundation website or Trees Are Good for more information on watering.

As a general rule, “Anytime you notice the soil is drying out, you want to start irrigating again,” Barar said.