Sissoo tree

Q & A: ASK THE EXPERTS

Q - I planted a sissoo tree last spring and it is now 10 feet tall. I water it for 2 minutes twice a week with a bubbler, and I haven’t fertilized since early last summer. Its leaves are turning yellow. What should I do?

A - Although non-native, the sissoo tree (Dalbergia sissoo) is popular in landscapes because it is well-adapted to our climate and soils, says Cathy Rymer, city of Chandler water conservation coordinator. Typically, this tree is semi-evergreen, losing some or most of its leaves in winter. The yellow leaves may simply be a response to cold weather, she notes.

Yellow leaves also could be a response to soils that are too moist. Because plants are unable to absorb iron in soggy soil, the resulting iron deficiency can cause yellowing leaves. Wait until late February or March before you fertilize, and that should be all the feeding your tree needs for the year.

Rymer also recommends adjusting the watering schedule. How often you water is very important to plant health. A good schedule for non-native trees in winter is to water deeply once every 2 to 3 weeks. Apply enough water with your bubbler so that the water soaks 3 feet deep.

You can measure depth with a probe or soil-moisture sensor (available at home-improvement stores or nurseries). The probe will be easy to push into moist soil but difficult to move through dry soil. If you are only able to probe to 12 inches after irrigating, you know that more water is needed. Here’s a link to schedules for watering landscape plants: chandleraz.gov/default.aspx?pageid=766.