Watering Trees During Drought

For people with oaks, I’ve written a more detailed article here on proper watering and care.

After five years of drought here in Southern California we have a tree crisis – in our city alone (Redlands) we have 1400 dead street and park trees. Some are young, but many are old ones that take decades to replace.

Many have been stressed by the continuing drought in California. In addition, well-meaning people have been removing lawns and changing to low-water landscapes — but their trees are not getting the water they need.

Here are some guidelines on watering your trees & useful resources: But first, a reminder of why trees are so important.

If you lose a large tree, you’ve lost:

• a valuable shade canopy
• property value
• important wildlife habit value
• plus energy conservation – did you know a single large trees cools as much as 10 room air conditioners?

What does a tree under “drought stress” looks like?

• Drought injury to trees can show up suddenly or may take up to two years. Symptoms include wilting, curling at the edges, and yellowing.
• Deciduous trees may develop scorch, have brown outside edges or browning between veins.
• Evergreen needles may turn yellow, red or purple. They may also turn brown at the tips of the needles and progress.
• In continued drought, leaves may be smaller, drop prematurely or dead ones may remain attached

How to water
All trees need deep watering. The amount depends on the tree’s age and species, and also soil type. But here are some general guidelines.

Young trees need at least 15 gallons of water each week. Two to three times a week is best during the first several years.

Mature trees need deep watering once to twice a month around the drip line, where the branch edges are. The water should soak down about eight inches. For example, run a drip irrigation or soaker hose for one hour. Other options are using a bucket with holes or watering by hose, or leaving a hose on at a low rate for several hours, moving it around the tree’s perimeter. You can water by hose any day of the week.

Even native trees like oaks need water to replace the rainfall that falls in a normal year. We’ve been in a drought for five years and trees haven’t gotten their normal rainfall.

Other tips

• MULCH! Spread 4” of mulch around the tree, but not next to the trunk. Use wood chips/bark, not stones or rocks which heat up.
• Don’t fertilize a tree that is drought-stressed.
• If you do pruning, remove dead or diseased branches, but overpruning causes more stress on trees during drought.
• Avoid heavy herbicide use around stressed trees.
• Irrigation hoses should spiral around the tree, starting at 9 inches from the trunk to just beyond the branch tips.
• Still have concerns? Consult an ISA certified arborist

For more info:

Watering Needs of Tree Species (Sacramento)

Claremont resources – Deep Watering Trees and Tree Watering Guide

Trees are undergoing stress in California’s drought; water with care (LA Times)

Pruning Guides from ISA (International Society of Aboriculture) on Palms and Mature Trees

Top 22 Benefits of Trees (TreePeople)