Containers Used in Single Valve Landscapes Drive the Irrigation Cycles

Q. We have a single zone (one valve) irrigation system in our yard with about 50 various plants. Plants include two mature olive trees. citrus, a dozen roses, flowerpots, and various bushes and cacti. We water the cacti by hand. We automatically water once a day, deeply, for about 20 minutes. Some friends of ours water three times a day and my son waters twice a day with no problems. Please comment.

Plants grown in containers in a landscape determine how frequently everything else on the same valve is watered. It is best that plants grown in containers are on a separate valve from plants grown in the ground.

A. The “flowerpot plants” determine how often a one valve irrigation system is turned on; its frequency. The plants in the flowerpots control when water is turned on or they suffer, and we see it. The remaining plants adjust to whatever daily watering schedule they are given. You are satisfied with this watering schedule. Everything looks good. How about your plants in the long run?

Container growing has alot of advantages but these plants must be watered often compared to plants grown in the ground.

            Watering in the desert is the “life blood” of a landscape. Plant roots grow best where there is the ideal mixture of water and air. A balance must exist between both, but not too much of either one if the plant is to be healthy and survive. Watering too often, or poor drainage, and the roots drown. Skipping a day when its hot, the plants suffer from drought.

            Watering daily encourages the roots of plants to grow near the soil surface. That’s where this ideal mix happens. Watering daily may be fine for small plants with shallow roots, but not for deep rooted trees like your olives or citrus. The larger plants prefer a lot of water applied at once (slowly or held in a reservoir around the tree) then no more applied water until half of that water is used. This irrigation strategy encourages deeper tree rooting, more tolerance to hot weather and better resistance to strong winds.

Two thoughts here. A container inside a container shades the interior one making the soil less hot in the summer. Wooden containers protect the soil from overheating better than clay pots. 

            So ideally for the plants, more irrigation valves are needed to encourage the deeper rooting of trees and shrubs. But if you are happy with how the plants look, satisfied with your water bill, want to use only one valve, and don’t care about tree health and longevity, then watering them once, twice or three times daily will work.

One irrigation valve and watering daily will work for watering an entire yard but it is not the best for the plants. 

If you haven’t done it, cover the soil with a layer of woodchip mulch to control weeds and conserve water. I have found that a layer of woodchips in the orchard allows one more day without watering as often in the summer months. As woodchips rot, roots of large trees have a bigger area to find places to grow. The olive trees can tolerate rock mulch, but woodchips for the citrus and roses works best in the long term.