Our urban forest (yes, the trees in your landscape are part of a forest) provides so many benefits too us – cooling, increased home values, beauty, and better mental health just to name a few.

Here’s what you can do to help keep your members of our urban forest as healthy as possible.

1. Water your trees to a depth of about two feet, because 95% of the tree’s roots are in the first two feet of soil.  To check if you are getting down to that two-foot optimum, insert a long screwdriver or soil probe into the soil around your tree a day after watering to determine the depth the water has reached.  Adjust your watering time, if needed, to reach that two-foot goal.

2. Water your trees a little inside and outside of the canopy edge (the outer ring of the tree’s leaves) because that is where the roots that take in water are located. 

3. Water deeply and infrequently for maximum tree health.  See the Summer Watering Recommendations for more information.

4. Check your trees for signs that they aren’t getting enough water: wilted leaves early in the morning, scorched leaf edges, twig die-back from the top down or a sparse leaf canopy. 

5. Take advantage of rainwater by directing downspouts or canales toward existing trees. Consider planting new trees in lower areas to take advantage of captured moisture.

6. Surround your trees with 4-6 inches of organic mulch. Organic mulch helps to retain soil moisture, keeps soil temperatures more consistent, and keeps weeds out. Additionally, over time it loosens compacted soil, adds organic matter, and slowly adds nutrients to the soil. Note: organic mulch does not include bark (sometimes called ‘bark nuggets’ or ‘deco bark”). Use actual wood chips like what comes out of an arborist’s woodchipper.  Many tree services offer wood chips for free and several local businesses sell wood chip mulches in bulk.

Author: Amos Arber, ASLA, ISA Xeriscape Incentive Inspector with the Water Resources Division for the Water Authority. Have a question about the article AskAnExpert@abcwua.org