Answer: How often you need to water depends upon soil type and weather, so I can't give you an exact answer. But, here's some information that might help you determine how often to water your trees:
Big trees have big root systems. With a few possible exceptions, big trees also use more water than smaller trees. In the wild, root diameters will average three to five times the height of the tree. In landscape situations, roots are generally two to three times the diameter of the canopy of the tree.
In our landscapes we need to at least irrigate half the area under the canopy of the tree to be adequate for its root system. If we don't, we run the risk of tree blowover in high winds ,and not giving a tree enough water and declining tree health as the tree gets bigger.
Drip emitters in most of our soils in the valley need to be about two feet apart under the canopy. When a tree is 20 feet tall it will need a circle of emitters about two feet from the tree trunk and the emitters two feet apart in the circle. Another circle is needed two feet from the first, emitters also two feet apart. Another circle of emitters is needed another two feet away from the second, and so on.
As you can see, large trees need a large number of emitters and at some point the number of emitters needed for one tree becomes nearly absurd. A 20-foot tree would need four to five circles of emitters.
It is much easier to put larger trees on what is called bubbler and basin irrigation system. Bubblers are high volume irrigation emitters, usually just one, that floods a basin around the tree called a watering basin. The volume of water is so fast that it floods this basin and the basin drains into the root system. As the tree gets bigger the basin can be enlarged and the number of minutes for the bubbler increased.
Drip emitters need to be on for an hour or longer to give the tree enough water. Bubblers can provide adequate water are in minutes.
Usually once a week is all that's required for a bubbler system.
Best wishes with your orange trees.
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