Our city is comprised of a few different types & mixtures of soils across our 36 sq miles. The following is a list of general guidelines for use when watering trees, especially during months without rainfall.

• The average tree requires approximately 160 gallons of water per month. This can be applied by running a soaker hose with a low flow of water for 15 to 20 minutes (equivalent to four 5 gallon buckets), two times per week.
• Watering should be applied at the dripline of the tree (outer perimeter of the tree foliage).
• Watering of trees is exempt from irrigation restrictions provided no water waste occurs. Spread mulch as far out as the branches reach (if possible), approximately three inches deep. Do not pile mulch against the tree trunk as this may rot the bark and trunk.
• Don’t dig holes in the ground surrounding the tree in an attempt to deep water as it will only dry out the feeder root system.
• Never assume that any tree can go without water, even “drought tolerant” species. We encourage the use of an in-ground irrigation system when possible.

Fun fact: Providing adequate water (160 gallons) per month will cost a property owner roughly $1.45, per billing cycle, at current rates.

What Does a Tree Under Drought Stress Look Like?

Drought stress symptoms can show suddenly or take up to two years. 

Typical symptoms include

• Leaf wilting/curling/yellowing
• Deciduous trees may develop “scorch” which is browning along edges or between leaf veins
• Leaves may be smaller than normal or drop prematurely.
• Evergreen needles may turn yellow, red, or brown, and may discolor all the way to the twig.

Other Tree Care Tips

• Use organic mulch around your tree to increase soil moisture, while keeping it at least 6” from the trunk.
• Consult/use a professional when pruning your trees; don’t over prune.
• Avoid fertilizing trees experiencing drought stress, as salts may further tax the tree.

Watering Young Trees

• For the first three years, young trees need slow, deep watering during the dry season typically April to October
• Water 2-3 times per week
• On average, a young tree will need 15 gallons of water per week.

Watering Mature Trees

• Mature trees need deep watering that penetrates at least 2-3 feet.
• Established drought-tolerant trees may need occasional watering at 1-2 month intervals in the dry season. California Native Oaks, California Laurel, Cork Oak, and Chinese Pistache can be damaged and short-lived with too- frequent summer watering.
• Moisture adapted trees benefit from an occasional deep watering to at least one foot 1-2 times a month. Some species are Birches, Redwoods, Magnolias and Red Maples

How to Water

• A soaker hose that circles the drip line is best. Other methods include:
• Timed hand watering using a spray attachment on the end of a hose
• Moving a slow running hose around the drip-line
• Moving a bucket with a hole in the bottom around the drip line
• Young trees can be hand-watered by the above systems, however
  • especially benefit from use of watering bags which deliver higher volume of water at a slow rate
• Remember – any deep watering is better than no water.  The water trees receive through lawn irrigation is not sufficient for most trees and can lead to shallow, more unstable roots.

Why Trees are Important

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

• Valuable shade canopy
• Property value
• Important wildlife habitat value
• Energy conservation
  • a single large tree cools  as much as 10 room air conditioners