Drought stress is killing California’s forests and urban trees. Check your trees for symptoms.

Wilting leaves

Yellow or brown edges on leaves

Orange or brown needles

Most vulnerable trees

Newly Planted Trees

New trees with a trunk less than seven inches in diameter also have a small root zone, limiting their access to water.

Trees in Confined Spaces

Trees planted between the street and sidewalk or other small spaces have a small area for roots to access water.

Trees in Lawns

If a property owner stops watering their lawn, trees located in the lawn require their own source of water.

How to water trees this summer

Even if you stopped watering your grass, continue to water your trees.

Watering rate

Watering rate
Water at the rate of one gallon per hour with a soaker hose, or with a dripline with an emitter every 24 inches. Make a circle with the hose or dripline at the outside edge of a tree’s canopy.

Length of hose needed
The distance around the outside edge of a tree’s canopy equals the diameter of the canopy (the distance from one side of the canopy to the other) multiplied by 3.14. For example, if the canopy diameter is 20 feet, you need 63 feet of hose (20 x 3.14 = 63).

Watering time

Soaker hose
A soaker hose will emit one gallon of water per hour per foot of hose

20 foot canopy = 3 hours
30 foot canopy = 4 hours
50 foot canopy = 5 hours

A dripline will emit one gallon of water per hour per emitter (every 2 feet)

20 foot canopy = 6 hours
30 foot canopy = 8 hours
50 foot canopy = 10 hours


When to water

Once every 2 weeks
Medium/moderate water use trees

Once a week
High water use trees

Reduce evaporation
Reduce evaporation between watering days by applying a 2-4 inch layer of mulch over the irrigated area.

The Benefits of Trees

Air Quality One acre of forest absorbs six tons of carbon dioxide and puts out four tons of oxygen / USDA

Water Quality California’s street trees catch 7 billion gallons of rainfall annually, reducing pollution from stormwater runoff / USDA

Energy Use Trees planted along the southwest side of a home or building can reduce air conditioning needs by 30 percent / USDA

Property Values Larger trees in yards and along street can add 3-15 percent to home values in the neighborhood / Wolf 2007

Rental Rates Office space rental rates were 7 percent higher in buildings with high quality landscape / Laverne & Winson-Geideman 2003

Sales Tax Shoppers claim they will spend 9-12 percent more for goods and services in business districts with a high quality tree canopy / Wolf 2005

Exercise A green environment may boost exercise frequency and enhance itse restorative effects / Hug 2009

Crime There is less graffiti, vandalism and littering in spaces with natural landscape than in spaces with no plants and trees / Brunson 1999

Roads Shade from trees can reduce the cost of resurfacing (slurry sealing) streets by 15-60 percent / McPherson & Muchnick 2005

Learn More


Selectree was developed by Cal State San Luis Obispo and lets you search for trees to plant based on a wide range of characteristics including height, shape, root damage potential and whether it’s a common allergan. Explore.

National Tree Benefit Calculator

Enter your zip code, the type of tree and the diameter of the trunk and this website will calculate the environmental and economic benefits the tree provides.

Arbor Day Foundation

The Arbor Day Foundation website will help you identify, choose and care for trees.
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