90% of desert homeowners don’t water their shrubs correctly. This stresses the plants, wastes water, and costs you money. Learn how to water the right way for beautiful, healthy desert shrubs.
Correct watering is probably the single most important thing you can do for your desert shrubs.
If your shrubs get too much water, they’ll have underdeveloped root systems and will be prone to breakage and disease.
If they don’t get enough, they won’t thrive and may even struggle to survive.
Unfortunately, learning how to correctly water can seem daunting but it all breaks down to understanding two factors:
- First is how often to water. This varies with the time of year.
- Second is how much water to give your shrub with each watering. This depends on the current size of your shrub and will change as it grows.
Here are charts that will help you determine how often to water and how much water to give your shrub with each watering.
How Often to Water Low Water Use Shrubs
Desert-adapted shrubs can be either native to the desert southwest, or they can originate in other dry parts of the world.
Examples of native desert-adapted shrubs include Texas ranger, fairy duster, hop bush, yellow bells, and globe mallow.
Examples of non-native desert-adapted shrubs that are commonly grown in the southwest include emu bushes, oleander, and bougainvillea.
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 – 45 days |
How Often to Water High Water Use Shrubs
Some shrubs that are grown as desert landscape plants are moderate-to-high water use. They can thrive here provided they get enough water.
Shrubs that fall into this category include bottlebrush, hibiscus, plumbago, and roses.
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 Shrubs
If you are watering a newly planted shrub, you need to water it more often. You can follow this schedule for the first two months.
| 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 shrub 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 Shrubs
This next chart shows you how much water to give a shrub with each watering, depending on the current size of its canopy. This stays the same with the seasons, but changes as the shrub grows.
Gallons per Diameter
| Diameter | 1′ | 2′ | 3′ | 4′ | 5′ | 6′ |
| Gallons/ Watering | 1 | 4 | 8 | 12 | 17 | 20 |
Water Deeply – What Does That Mean?
You’ll often hear that you should water deeply. For shrubs, the general rule of thumb is that you want to water to a depth of 2 feet.
And be sure to water at a shrub’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 outward as the shrub grows.
One way to make sure you’ve watered to a depth of two 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.
Water Saving Tip!
Anytime 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 an irrigation system installed at their home, or they choose not to use it and water manually, either with soaker hoses or hand-watering.
Here’s how to water your shrubs both ways.
Irrigation Systems
If you have an irrigation system, your use of math skills has just begun!
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 options for where you can find 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 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 many rely on the default of 20 minutes every 3 days.
Manual Watering
If you don’t have an irrigation system, you can water your shrubs with a soaker hose, spiraled around the drip line, or a hand-held sprayer.
To make sure your shrub 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 of 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 shrub.
Let’s say your shrub has a 3-foot canopy and so, according to the chart above, you should give it 8 gallons per watering.
The basic formula is:
gallons per watering ÷ flow rate = how long to water
So in this example, you would divide the 8 gallons by the flow rate (3 gallons per minute) to determine how long to let your soaker hose run.
8 gallons per watering ÷ 3 gallon per minute flow rate = 2.7 minutes
Another way to figure out your flow rate is to put a water flow meter on 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 (and every shrub’s) situation is different depending on a multitude of factors such as:
- What is the shrub’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? I
- 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 shrub is getting too much or too little water, feel free to adjust 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.
