Even though California's majestic oak trees are generally considered drought tolerant, the last four years of well-below-average rainfall are taking a toll, reported the Sierra Sun Times.

"In some parts of the state, oaks are being deprived of water for as long as nine months, creating extreme water stress," said Greg Giusti, a forest and wildlands advisor for UC Agriculture and Natural Resources. Giusti is headquartered in the UC ANR Cooperative Extension office in Mendocino County. 

Giusti and Kris Randal, the UC Master Gardener coordinator for Mariposa County, suggest that California residents with oaks on their property give the trees a good soaking once a month during the summer.

The water should be applied around the drip line - the area below the outstretched branches - but not near the trunk. A permeable soaker hose is an ideal tool for slow application over the wide area. Allow the water to run until it has soaked down to a depth of 12 to 18 inches, which can be detected with a long probe such as a screwdriver. "If it comes up with signs of moisture at the tip, you're good," the article says.

Randal said it is important to let the soil dry out completely between waterings, because oaks are susceptible to root fungus that can grow in warm, damp soil.

Even if water is unavailable and the leaves begin to turn brown or fall, the experts suggest waiting for spring before considering removing the tree.

"If you tree leafs out, it's still alive," Randall said. "And in this drought, give it extra time to leaf out."

A large blue oak in Mariposa County.