Water & Drought

Can young trees survive on weekly irrigation?

Q: Our roots are firmly planted in old East Sacramento, where many new trees have been planted when mature, sickly Modesto ash trees were lost. Can our younger trees survive the summer months with once-weekly deep-root watering? And should an older, somewhat sickly tree providing shade be removed to conserve water? – Heidi Boyd, Sacramento

A: Once-weekly deep watering will be important to those trees’ health. And yes, they will survive, even thrive with that approach.

“Deep” watering is key, says Sacramento certified arborist Matt Morgan of Davey Tree Expert Co.

“The top 12 inches of soil is where the roots are,” Morgan said. “Most people run their sprinklers for 7, 8 minutes; that only reaches the top two inches of soil. You need the water to go deeper.”

Instead of relying on sprinklers, individually irrigate the trees with a hose and let the water slowly percolate into the soil. “It could be four hours, depending on the flow rate (of the hose),” Morgan said. “In most cases, it’s at least 30 minutes.”

Take a soil probe or long screwdriver to see how deep the water reaches.

Drought stresses trees and that stress accumulates, he noted. Your sickly tree may already show signs of that stress. But a good mature shade tree may be worth saving. Before chopping it down, bring in a certified arborist for an evaluation, Morgan suggests.

“Once you have stress, it opens a tree to secondary issues such as disease or pests,” he said. “It’s a downward spiral until you catch it and start making corrections.”