(Last updated December 5, 2020)
I’ve always wished there were a simple formula that could tell us how much and how often to water an avocado tree. Alas, the variables are too numerous and complex: weather is ever-changing, different soils have different water-holding capacities, frequencies are partially determined by the watering method (drip, sprinkler, etc.).
Yet I bulled forward and made this table anyway, showing approximately how much and how often to water avocado trees of four different sizes in each month of the year.
Even though such a table cannot be perfectly accurate, it’s pleasantly usable. Even if you follow the table blindly without making any adjustments, your tree is likely to do well.
If you are interested in being more efficient and effective, read on about how you can tailor the application of the numbers for your particular conditions, as well as to learn about how I created the table.
Important note: Be sure you’ve planted your avocado tree properly and watered it through its first couple months properly before starting to use this table.
Gallons are for the valleys
How did I come up with these numbers of gallons? I used weather information that is similar to where most people in Southern California live — basically, the valleys: roughly five to fifteen miles away from the beach. (Specifically, it’s Zone 6 on this map.) Anaheim in Orange County is an example of a city in this zone.
If you live closer to the ocean, well, aren’t you cool and comfortable? And so is your avocado tree. You can give it 10% less water in the summer. Likewise, if you’re more than fifteen miles from the ocean, your avocado tree feels the heat and probably needs 10% more gallons than the table shows for the summer months. (Your tree might also need to be watered a bit more often.)
But these numbers aren’t just theoretical. They are also based on the quantity of water that I have found to work well on my own avocado trees.
(Here is a video showing how I water my avocado trees.)
In my experience, you can’t give avocado trees much less water without them suffering. (I’ve tried.) And it’s unnecessary to give them much more. (You won’t get more fruit, which is the point.)
One exception that I must note is when an avocado tree, especially a young avocado tree, is growing near a large tree, shrub, or vine. That large plant will often grow roots into the zone where you are watering your young avocado tree and suck up some of its water. Therefore, you may need to water the young avocado tree more, even much more, than the table shows for its size. Keep an eye out for this.
Frequencies are for sprinkling and mulch
The table makes a couple of assumptions. One is that you are sprinkling or spraying the water under the tree, not using drip emitters. If you are using drip emitters, then the gallons don’t change but the frequency does. You must water more often with drip, probably every two or three days in summer.
Another assumption is that there is mulch under your avocado tree. Leaves or wood chips under an avocado tree are extremely beneficial in myriad ways, one of which is allowing the tree to go longer between waterings.
What did I base the table’s frequencies on? Mostly, I based them on what has worked for my trees, as well as what has worked on trees in yards and commercial orchards that I have visited throughout Southern California.
In addition, if you’re familiar with the concept of evapotranspiration (ET), then you might be interested in knowing that the table says to water after between one-half and one inch of ET has been reached. I’ve found that trees tend to need water at about the half-inch ET frequency in late summer, but they only need water at about the one-inch ET frequency in late winter. I believe this is due to the winter rains having wetted all the soil around the trees at this time.
If you want to be extra efficient with watering (especially during the fall, winter, and spring, when the weather is variable), you can find a CIMIS station near you to get actual ET readings. See more on this in my post here.
Please remember that the frequencies in the table are averages and are meant mostly as a point of reference. You must take into account rain that falls in winter, for example. And you should certainly not wait until it has been three days before irrigating again in August if there is a heat wave and your tree is wilting under 110-degree sunshine.
(See more about a situation like this in my post, “Protecting avocado trees from heat.”)
No automatic watering in winter
Where avocados grow wild, winters are even drier than ours in Southern California. So once our rains begin, sometimes in November but more reliably in December, you should stop watering your avocado tree automatically.
Unnecessary irrigation in the winter not only wastes water but more importantly can keep the soil soggy and disease prone. After we’ve had our first couple inches of winter rain until around the end of March, only water an avocado tree if there is a dry spell of about a couple weeks.
And when you do water, give the tree approximately the amount it has used in that interval according to the table. For example, a 10-foot tree in February that has received no rain for two weeks needs to be given about 56 gallons.
Big trees get water elsewhere
The table only goes up to 15 feet because bigger trees in a normal yard will have grown extensive root systems that drink from neighboring plants, maybe even from your neighbor’s plants. So if you have a big avocado tree, you almost surely can give it less water than an avocado farmer would have to give such a tree in an orchard.
It’s impossible to say how much to give your big tree. Just think about what is being watered under its canopy and even within ten feet or so of the outer edge of its canopy. If there are irrigated plants all over that area, then you might not need to give the tree any water of its own. This is particularly true if there is lawn being watered within the tree’s reach.
An example from my yard
This is a Lamb avocado tree in my yard that has a canopy diameter of 9 feet as of December 2020. The sprinkler that I use on this tree puts out 12 gallons per hour. I usually water the tree for two hours at a time. Last summer, during July, I watered the tree for a total of 28 hours, and I watered it about every two or three days. The average volume I gave the tree in July was 10.8 gallons per day.
If you look on the water table, it says that a 10 foot (diameter) tree should get 10.3 gallons per day, and it should be watered every three days. My yard is in Ramona in San Diego County, a slightly hotter and drier location than the zone used for the table. Therefore, giving my tree about 10 percent more water and irrigating it a bit more often makes sense. And it is effective: as you can see, the tree is healthy with little to no tip burn on its leaves here in winter.
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