Chinese Pistache Should Never Be Watered Daily After Planting

 Q. I purchased a Chinese Pistache one year ago that was about 12' tall; not a small tree. Everything was fine until July, about 11 months after planting.  The leaves went from deep green to dry and crunchy, quickly.  The tree was watered twice a day for 25 minutes during the summer. The supplier of the tree told me it was insect damage and to water once a day for 45 minutes longer. My concern is that all the landscaping is on the same zone. It is all doing extremely well. The landscaper has recommended 20-25minutes/ twice per day. I’m confused because I was told that what will kill the tree is if the soil is too wet.

Chinese pistache tree recently planted.

A.  Your watering schedule is very confusing. Part of the confusion is that everything is watered the same.  In landscapes, trees and shrubs should be watered separately from those plants requiring daily irrigations. In other words, trees and shrubs are watered separately from those requiring daily waterings. Daily summer irrigation is required only by lawns, flower beds and vegetable gardens.

Instead put a donut or moat around the tree to force more water toward its roots.

The frequency of irrigation (on and off) is only controlled by the irrigation valves. Irrigation valves do not control the amount of water plants receive. The amount of water they receive is controlled by the size and number of irrigation emitters. Trees and shrubs are deeper-rooted; the amount of water they receive should only be controlled by irrigation emitters. The amount of water each plant receives depends on its size.  Larger plants require more water than smaller plants.

Irrigation controllers dont have to be as fancy as this one. Figure out what you need it to do. The primary function of an irrigation controller is to turn irrigation valves on or off.

Never plant anything living in a “dry” hole regardless of the time of year it’s planted.  The hole should always be moist or at least “mucky” when planting.  After planting is finished, give the soil a chance to start drying before watering again. This should be at least one day except when planting in pure sand.

If your trees and shrubs are watered the same as everything else in the landscape, it is being watered wrong.  There should be at least two irrigation valves; one irrigation valve is needed for summer daily irrigations, and the second valve (or other valves) is needed for watering everything that is not watered daily in the summer. Notice I said at least two irrigation valves.

Your landscape probably needs more than two.

            Next, connect an irrigation valve to those plants requiring daily summer irrigations (lawn, flower bed, vegetable garden;). These are the only plants connected to this valve. Reserve the second valve for bigger plants needing nondaily irrigations.

At planting time, dig the hole for plants three times the width needed to just barely fit the plant in the hole. Not just a hole big enough to fit the plant in and call it done. This is the desert. Soils need to be amended for planting and the planting hole needs to be wide, not necessarily deep.