As the weather cools in fall and the citrus fruit on my trees start turning from green to yellow, they catch my eye. It’s been so long since I’ve eaten a tangerine or a navel orange. I can’t wait until this new crop is ripe.
And I look at the amount of fruit on the trees and the amount of new growth, and I ask myself if I’ve been watering enough. Or have I been watering too much? How much have I been watering to get the results I’ve got?
I keep records of my irrigations and I use drip emitters so it is easy to do the calculations. So I did them.
After doing them, I compared the numbers to those in a table by UC Riverside researchers (for the Riverside area). Wow! I water way less than they recommend. I don’t know how they came up with their numbers, but I know that I would be wasting a lot of water if I used their table, and I might be causing problems in my trees as well.
My watering table
Here are my numbers. This is about how many gallons my citrus trees get in order to perform the way they do:
Over the years, I have gotten good performance from my trees while watering them anywhere from daily to every two weeks (in summer). Last summer, I watered most of my citrus two times per week (on drip). Citrus trees are comfortable getting water in a broad range of frequencies.
When choosing my frequencies, I keep a few things in mind. Young trees need water more often than old trees. And if you use drip irrigation, you need to water more often compared to sprinklers or bubblers (with proper basins).
Your watering table
How can this table be of use to you? First, you have to compare your location to mine. I am in Ramona, San Diego County, which is within Zone 9 of this evapotranspiration map. Other cities in this zone are Valley Center, Redlands, Rancho Cucamonga, and Simi Valley. If your citrus trees are in a cooler or hotter spot, then adjust accordingly.
Use this spreadsheet made by Yard Posts Supporter, Robert M., which can instantly adjust my watering table for different zones in California.
Also note that rain is not accounted for. Any time we get rain of at least 0.5 inches, the irrigation the citrus trees need is reduced. In practice, I only occasionally find the need to give my citrus trees any irrigation from December through March.
Pay attention to the plants surrounding your citrus tree. Sometimes there are bushes or other trees that drink some of the water you give your citrus tree, thereby requiring that you add more.
Judge your watering by the look of the trees. Are they growing? Is the fruit getting to the expected size?
It’s my observation that most citrus trees in Southern California are watered too much rather than not enough. Overwatering citrus seems to be the most common inclination.
That said, if your citrus tree is not getting enough water it will display its thirst by folding its leaves more than normal.
(For help in reading other symptoms in citrus leaves, see my post: “Reading citrus leaves.”)
What I’d love to see more people do is find the water needs of their citrus trees by backing off the water until the trees show leaf fold. Find that lower limit. Fruit and the health of the trees will not be sacrificed by testing this, as long as you irrigate soon after the tree shows its thirst.
Citrus trees are tough, especially as they age. I have deliberately backed off on the water to many of my citrus trees in order to test this and found no lasting damage while reaping the benefits of knowing how much water my trees really need.
(See this post for an extreme example: “Unirrigated fruits and vegetables.”)
Please share with me your results if you explore this with your citrus trees.
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