90% of desert homeowners don’t water their trees correctly. This stresses the plants, wastes water, and costs you money. Learn how to water the right way for beautiful, healthy desert trees.
Correct watering is probably the single most important thing you can do for your desert trees.
If your trees get too much water, they’ll grow unnaturally fast and will be prone to breakage and disease. If they don’t get enough, they won’t thrive and may even struggle to survive.
If you give your trees a little bit of water frequently or neglect to move your emitters away from the trunk as the tree grows, your tree’s roots won’t grow wide and deep enough to anchor that tree, making it prone to storm damage.
Unfortunately, learning how to correctly water can seem daunting, but it all breaks down to understanding two key factors:
- First is how often to water. This varies with the time of year.
- Second is how much water to give your tree with each watering. This depends on the current size of your tree and will change as it grows.
Let’s look at each of these factors in depth.
How Often to Water Low Water Use Trees
Desert-adapted trees can be either native to the desert southwest, or they can originate from other dry parts of the world.
Examples of native desert-adapted trees include desert willow, palo verde, ironwood, and native mesquites.
Examples of non-native desert-adapted trees include fruitless olive (Mediterranean), willow acacia (Australia), and Chilean mesquite (South America).
Regardless of their origin, these trees are all considered “low water” use. Here’s a recommended watering schedule for low water use trees.
Low Water Use Schedule
| Season | Frequency |
| Spring (March – May) | 14 – 30 days |
| Summer (May – Oct.) | 7 – 21 days |
| Fall (Oct. – Dec.) | 14 – 30 days |
| Winter (Dec – March) | 30 – 60 days |
How Often to Water High Water Use Trees
Some trees that are grown as desert landscape plants are moderate-to-high water use. They can thrive in the desert provided they get enough water.
Most are non-natives such as Chinese pistache (Asia) and lemon bottlebrush (Australia). However, some are natives that come from riparian regions of the southwest, such as Arizona ash.
Here’s a recommended watering schedule for moderate to high water use trees.
High Water Use Schedule
| Season | Frequency |
| Spring (March – May) | 7 – 10 days |
| Summer (May – Oct.) | 5 – 7 days |
| Fall (Oct. – Dec.) | 7 – 10 days |
| Winter (Dec – March) | 10 – 14 days |
How Often to Water New Trees
If you are watering a newly planted tree, you need to water it more often. You can follow this schedule for the first two months.
New Tree Watering Schedule
| Weeks 1 & 2 | Every 3 – 4 days |
| Weeks 3 & 4 | Every 6 – 7 days |
| Weeks 5 & 6 | Every 7 – 10 days |
| Weeks 7 & 8 | Every 10 – 14 days |
There is no point in giving your newly planted tree any more water than is needed to soak the root ball, since it hasn’t had time to grow new roots.
How Much Water to Give Desert Trees
These next charts show how much water to give a tree with each watering, depending on the current size of its canopy. This stays the same with the seasons, but changes as the tree grows.
Gallons per Canopy Size
| Canopy | 1′ | 2′ | 3′ | 4′ | 5′ | 6′ |
| Gallons/ Watering | 1.5 | 5 | 11 | 16 | 22 | 26 |
| Canopy | 8′ | 10′ | 12′ | 14′ | 16′ |
| Gallons/ Watering | 38 | 59 | 85 | 115 | 150 |
As the tree grows, you will need to add emitters and move them away from the tree trunk and towards the drip line.
Watering Citrus: A Special Case
Correctly watering citrus trees is a little more complicated and depends on the age of your tree, the time of year, and canopy size. A University of Arizona publication, Irrigating Citrus Trees, covers everything you need to know to figure out your trees’ water requirements.
Water Deep and Wide – What Does That Mean?
You’ll often hear that you should water deeply. For trees, the general rule of thumb is that you should water to a depth of 3 feet.
But it’s equally important to water wide, and that means watering at the tree’s drip line. Too many people start with irrigation emitters next to the trunk and that’s where they stay. They need to be moved away from the trunk (and their numbers increased) as the tree grows.
You may have heard that a tree’s root system is as big as the tree canopy, but that’s an understatement. According to the University of Arizona, a mature tree’s root system will spread 1.5 to 4 times beyond the width of the tree canopy!
And it’s estimated that 90% of tree roots are found in the top foot of soil where oxygen, water, and nutrients are readily available and essential soil microbes reside.
One way to make sure you’ve watered to a depth of three feet is to physically check using a soil probe. You may or may not have luck with this. I’ve tried and no matter how soaked the ground is, I hit too many rocks to get the probe down more than a few inches. If this happens to you, simply use the “Gallons Per Canopy Size” chart.
Water Saving Tip!
If at any time you receive more than 1/2″ of rain, you can skip the next watering.
Two Kinds of Watering Systems
There are two main ways to water landscape plants. The majority of homeowners rely on built-in irrigation systems. Some people don’t have them installed at their home, or they choose not to use them and water manually, usually with soaker hoses.
Here’s how to water your trees both ways.
Irrigation Systems
If you have an irrigation system, get ready to do some math!
If you take care of this yourself, you can find more information on how to set up your irrigation system to meet these goals in this excellent document that everyone with a yard should have: Landscaping Watering By The Numbers.
Here are a few places to access a digital copy:
And if you really prefer a physical copy, you can request one from Water Use It Wisely.
If you work with a knowledgeable landscaper or irrigation technician, you can give them this information and have them set it up accordingly. Some landscapers and irrigation technicians know how to set a system up properly, but most unfortunately rely on the default of 20 minutes every 3 days.
Manual Watering
If you don’t have an irrigation system, you can water your trees with a soaker hose, spiraling around the drip line.
Unless you have small new trees, watering with a hand-held sprayer is not practical. Sprinklers are not a good idea either since they waste a lot of water.
To make sure your tree gets the right amount of water per watering, you will need to figure out the flow rate, i.e., how much water comes out of your faucet per minute.
You can easily figure it out using a gallon bucket. Here’s how.
Step 1
Set up your soaker hose like you usually do to get a nice slow drip. Make note the position of the faucet handle – this is important! (I found that I keep the faucet handle turned to 9 o’clock when I use my soaker hose.)
Step 2
To figure out your flow rate, put a gallon bucket directly under the faucet, turn it on with the handle in the same position that you usually run your soaker hose (in my case, at 9 o’clock), and time how long it takes to fill.
How many gallons flow through your soaker hose in a minute is your flow rate.
I found it takes 20 seconds to fill a gallon bucket. This gives me a flow rate of 3 gallons per minute.
Once you know your soaker hose’s flow rate, you can figure out how long to water any tree.
Let’s say your tree has a 5-foot canopy and so, according to the chart above, you should give it 22 gallons per watering.
The basic formula is:
gallons per watering ÷ flow rate = how long to water
So in this example, you would divide the 22 gallons by the flow rate (3 gallons/minute) to determine how long to let your soaker hose run.
22 gallons per watering ÷ 3 gallon per minute flow rate = 7.3 minutes
Another way to determine your flow rate is to attach a water flow meter to your spigot.
Watering “Guidelines” Are Not Rules
Keep in mind that this information should be considered guidelines rather than rules and are not meant to be followed blindly. You know your unique situation better than anyone which makes you the expert on your garden.
Everyone’s situation is different depending on a multitude of factors such as:
- What is the tree’s microclimate like? Is it windy? Is it near a hot wall? Does it get any shade?
- What soil type do you have (clay, sand, rocky)?
- Do you water manually or have an irrigation system?
- Is your yard a mature garden with a thriving ecosystem? Or are you starting from scratch in a new construction home?
If at any time you see evidence that your tree is getting too much or too little water, of course you should adjust your watering schedule accordingly.
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Author Bio
Deane Alban is the creator of Southwest Gardener. She is a science writer with a bachelor’s degree in botany from the University of South Florida. Gardening is her lifelong passion. She’s been gardening in Tucson for 15 years.
