How Much Water Do My Plants Need?

“How much water do my plants need?”

I am often asked this question by desert dwellers and my answer is always, “That depends.”

There are several variables that determine how much water plants need, along with the frequency of watering.

Variables include:

• Type of soil (clay, sand, combination)
• What kind of plant (native plants, higher water use flowering shrubs and ground covers, succulents, etc.)
• Recommended depth of water
• Desert region (low-desert, mid-altitude, high desert)
• Efficiency of irrigation system
• Water pressure (can vary between neighborhoods)

As you can see, there is no universal watering guideline in regards to how long to water or how often.

Let’s look into the variables a little more closely to help you determine what yours are:

Soil – Clay soils hold onto water longer than sandy soil. They take longer for water to permeate to the recommended depth. The result? Clay soils need irrigation less often than sandy ones but need to be watered for a longer length of time. Phoenix area soil tends to have more clay in them while those in the Palm Springs area are sandy.

Plants – Native or desert-adapted plants need less frequent irrigation versus those that come from tropical climates. Cacti and other succulents do well with infrequent irrigation.

Water Depth – Trees need to be watered deeply while ground covers and succulents do fine at a more shallow depth – shrubs fall in between the two.

Desert Region – Where you live in the desert matters when it comes to water and your plants. The differences include rainfall amounts, when the rain falls, high and low temps, and more. Residents of low-desert cities like Palm Springs and Phoenix need to add water to their plants more often than those who live in higher elevation regions such as Tucson.

Irrigation System – The older your irrigation system, the less efficient it is. This is due to mineral build-up within the system, which affects the amount of water that comes out. Also, old drip irrigation systems tend to accumulate leaks. The average lifespan for a drip irrigation system is 10-15 years. 

Despite these differences, what is a shared characteristic is that the vast majority of desert residents water too often and not deeply enough. This is usually due to lack of knowledge and thinking the ‘more is better,’ especially in the desert.

Landscapers are generally not a reliable source when it comes to scheduling irrigation – most recommend irrigating far too often.

So what is a desert dweller to do?

Thankfully, there is very useful information available for homeowners to help them figure out when and how much water their landscape needs.

Major metropolitan areas throughout the Southwest have excellent watering guidelines available for residents. The guidelines include the regional variables we have discussed so far.

Here are helpful links based on major desert cities (click the link for the city closest to you):

Las Vegas

Palm Springs

Phoenix

Tucson

Watering guidelines are just that – guidelines. Circumstances may mean that you need to water more or less often, but these guides are a useful baseline to work from.

*One final note – before you implement a new irrigation schedule, it’s important to gradually wean your plants to the new one over several weeks. The reason for this is that it allows plants to become accustomed to the new schedule.

Yes, it does take a little work to figure out how much and often to water your plants, but these guides are incredibly helpful and will guide you along the way.

Noelle Johnson, aka, 'AZ Plant Lady' is a author, horticulturist, and landscape consultant who helps people learn how to create, grow, and maintain beautiful desert gardens that thrive in a hot, dry climate. She does this through her consulting services, her online class Desert Gardening 101, and her monthly membership club, Through the Garden Gate. As she likes to tell desert-dwellers, "Gardening in the desert isn't hard, but it is different."