How Many Days between Waterings in the Winter?

Q. I am not sure how long some of my trees can go without water during the winter. I have a mature Pepper, Mesquite and some palms that I have not watered for 10 days because of the cold temperatures. Is 10 days between watering okay?

A. 10 days between waterings should be no problem for trees and large shrubs provided they were given a deep watering prior to this. Deep rooted plants, like most trees and large shrubs, can go without water for a longer period of time than smaller plants. Deep watering means flooding the soil with water to a depth of 2 to 3 feet. If drip is used then making sure enough volume of water is applied to soak to a depth of 2 to 3 feet.

Applying water with drip emitters this close to the trunk is okay for the first couple of years. As this tree gets larger, more emitters will be placed underneath the canopy of this tree and further from the trunk. About half the area under the canopy should receive water. Apply enough water in a single application to wet the soil to a depth of 2 to 3 feet.

Many landscapes have small plants and big plants on the same circuit or valve. This means the small plants cannot be watered separately from the larger plants. The small plants require water more often. This forces the larger plants to be watered frequently even when they don’t require it. 

This twisted Acacia would be considered a desert tree. Putting a tree like this on an irrigation circuitFor desert plants gives greater flexibility when applying water. Applying water more often causes it to grow faster, larger and more dense. Applying water less often keeps it smaller, growing more slowly with fewer leaves.

Secondly, plants that do not originally grow in desert climates must be watered more often than plants which do. The mesquite and California pepper are both desert-type trees where water can be withheld for long periods of time with no problems. Palms are more shallow rooted and require water more often. But ten days is not too long for any of these plants during the winter.

In an ideal world the deeper rooted plants would be on a separate irrigation circuit or valve from shallow rooted plants. Deep rooted desert plants like acacia, palo verde and mesquite would be on a separate circuit from the other non desert deep rooted trees and shrubs. This gives you alot of flexibility in watering. 

Palo Verde is another desert tree whose growth can be managed by applying more or less water. Putting desert trees and shrubs on their own separate irrigation circuit gives you this type of flexibility.

The deep rooted plants would include trees and shrubs and deep-rooted woody perennials that die back each year such as Bougainvillea. The shallow rooted plants would include annuals and flowering perennials that die back each year like Lantana. Lawns should be on a separate circuit but could be tied into vegetables as long as the water could be turned off to vegetables between seasonal plantings.