6/19: All SBPL locations will be closed on Wednesday, June 19 for Juneteenth.


5/21-7/14: Eastside Library will be closed due to construction work.


Tree Watering


Trees offer several environmental and community benefits. Losing a tree can be like losing an investment, as it takes many years for trees to reach a maturity level where we can capture those benefits.

Tree Watering Dripline

How much should I water my tree?

Watering your trees is not always an exact science. We recommend you run a test to ensure that water is soaking in deep enough to reach your tree’s feeder roots. To be sure you are watering long enough, follow the steps below. You can also track how many gallons of water this will require by checking your meter. See below for details:

1. Check your meter before running your irrigation so that you can measure how many gallons you will need. Record the number on the meter. For your measurement to be accurate, make sure no other water is running in your household.

2. Turn on your irrigation for 30 minutes. Make sure you are using either a soaker hose or inline drip to water the area around your tree’s drip line. See the diagram to the right to find this area.

3. After 30 minutes, use a soil probe or dig down to test the soil. For a mature tree, the water must reach 18 inches deep. Based on how deep the water reached after 30 minutes, you can estimate the time required for you to effectively water your tree.

Example: If you test the soil and find it is dry deeper than 6 inches, then you know that your tree is only getting one-third its water requirement. Based on this, you will need to water your tree for 90 minutes total. This can be done all at once or over a few days.

4. Check your meter after running the irrigation for 30 minutes and record the new number. Subtract the first number you recorded from this new number to get the difference. Your meter measures water in cubic feet. One cubic foot is equal to 7.48 gallons of water, so multiply the difference by 7.48 to determine how many gallons of water were used in 30 minutes.

Example: If the difference that you calculate is 50 cubic feet, simply multiply 50 by 7.48 to get the number of gallons used (50 x 7.48 = 374). If you need to water for 90 minutes total, then this will require 374 x 3 = 1,122 gallons of water total, or 1.5 HCF billing units (1 HCF = 748 gallons).

How can I save water and keep my tree healthy?

  • Learn how to use your meter to measure how much water your tree needs to be healthy. Use the steps above to find the gallons required for your tree.
  • Spread your watering out over a few days. Mature trees need to be watered once a month. If your tree needs to be watered for 3 hours total, then you can water all at once or over a few days. If you are budgeting your water use to keep your bill down and save money, then spread your watering days out over two billing cycles.
  • Use a timer to keep track of watering. There is nothing like the feeling of realizing you have left your soaker hose on overnight, or seeing the bill that follows!
  • Add mulch. Adding a thick layer of mulch around your tree will keep soil moisture in, reduce evaporation and watering times. City water customers can receive 2 free deliveries of County mulch every 12 months.
  • Use graywater to water your trees. Laundry-to-landscape graywater systems reuse clothes washer water for your landscape. You can also save water collected in your shower to water your trees. Some trees are more sensitive than others to soaps and detergents, research the sensitivity of your tree species before applying this water.

Trees can show signs of stress for several reasons. If you have questions about your tree, contact an arborist.


Tree Watering FAQs

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