During drought, the goal for tree and shrub irrigation is twofold; reduce water use to save precious water and money, yet use enough water to preserve your substantial investment in your landscape trees and shrubs.

To irrigate trees and large shrubs within a lawn area, apply water from tree trunk taper to a little beyond the “dripline”, not directly on the trunk.  The dripline is the area directly below the outermost reaches of the branches. This is where the feeding root system of a tree or shrub is located, 6-9 inches below the surface.

Simply lay a slowly running hose on the ground and move it around the dripline as each area becomes saturated to a depth of 6 to 9 inches. Use a screwdriver to penetrate the soil for moisture depth measurement (when area is watered effectively the screw driver should push down to 6-9 inches with little or no resistance).  For large trees, this watering technique may take several hours.

In the continued absence of significant rainfall, large trees and shrubs will benefit from a twice a month watering to help them survive drought and heat.

Rule of Thumb:

Go up 3-4 ft on tree and measure the truck diameter (straight across not all the way around).

For every inch of diameter the tree needs 10 gal of water.

Ex: 10 inches in diameter= 100 gal of water.

New tree: 1 year or less.

Water the tree in such a way on a weekly basis.

Established Tree: 1 year or over.

Water the tree in such a way every 3 weeks. So divide the number by 3 and water with that amount on a weekly basis.

Note: In extreme drought environment water a new tree (twice weekly in such a method).  Established tree (twice a month in such a method).  This system is not exact science but has shown to be effective.