Correct watering is the single most important thing you can do for your landscape plants, including cactus. Cactus are often watered too much, too little … or not at all. These tips will help you water your cactus correctly to optimize their beauty and health. It might also save you money on your water bill.
There are a lot of ways gardening is different in the desert, and watering is one of them. And the usual guidelines for watering desert trees, shrubs, and perennials, don’t apply to cactus. So it’s easy to be uncertain about how to water your cactus or whether you should water them at all!
Watering cactus is pretty simple, and you don’t have to do it very often, but there are some fine points you might not be aware of that can make a big difference to your plants. Watering correctly will help you have healthy plants that look their best and are resistant to pests and diseases.
(Note that these tips can also be applied to other landscape succulents such as agaves, aloes, yuccas, euphorbias, desert spoon, and hesperaloe. The exception is #3 since not all succulent roots go wide.)
#1 Water Infrequently
While cactus are low water plants, they are not “no water” plants. They can survive for long stretches without water, but appreciate occasional, generous watering.
Too much water can be as detrimental as too little. Overwatered cactus can develop root rot, topple over, or even split wide open.
When in doubt, it’s always better to
underwater than overwater cactus.
#2 Change with the Seasons
Don’t water cactus on the same schedule all year. Your cactus needs more water in summer and much less in the winter.
Here are general guidelines for how often to water cactus planted in the ground.
| Spring & Fall | Every 3-5 weeks |
| Summer | Every 2-4 weeks |
| Winter | Only if no winter rains |
Any time you receive more than 1/2″ of rain, you can skip the next watering.
Many gardeners grow substantial succulents in containers as focal points. For these specimen plants, you can follow this schedule.
| Spring & Fall | Every 7-10 days |
| Summer | Every week |
| Winter | Every 2-4 weeks |
#3 Water “Deep Enough”
You’ve probably heard that you should water your plants deeply. You may have heard that from me, since I occasionally mention it here. 😉
While this advice applies to non-succulents (i.e., trees, shrubs, etc.), cactus are the exception. There’s no need to water them deeply… but you do need to water them “deep enough.”
Cactus have shallow root systems, rarely more than a foot or so deep, so watering to a depth of 18″ is more than adequate. But you also need to water wide.
#4 Water Wide
There’s a myth that refuses to die — that desert plants, including cactus, have long tap roots that grow deep to get water from the aquifer. But this is not true. Tap roots’ primary purpose is for anchoring, not water absorption.
Plant roots actively seek out water and grow towards a water source. So cactus roots spread outward, close to the surface to capture rain water. Most cactus have root systems that are wider than the plant is tall.
Watering Rule of Thumb!
Water cactus at an imaginary drip line that’s the same radius as its height.
For example, to water a 5 foot tall cactus, water 5 feet away from the base.
Saguaros, a Sonoran Desert keystone species, has been widely studied and so a fair amount is known about the root system of these iconic plants and how they use water.
Saguaros are 85% water and can hold up to 200 gallons of water in their tissues.
They have an anchoring tap root that are normally 2+ feet long, but the majority of roots are found within the top 4 to 6 inches. These surface roots can extend as far as 100 feet!
It makes a lot of sense that a plant would not put its energy into growing downward — have you ever tried to dig a deep hole in desert soil? It’s tough!
Here in Tucson, plant roots would have to go down hundreds of feet to reach water. And that’s not happening.
Additionally, the top foot of soil is the most desirable for roots — it’s where oxygen, water, and nutrients are readily available and essential soil microbes reside.
#5 Stop Watering in Winter
Cactus rarely need supplemental water during the winter, unless there have been no winter rains. Cactus do not like cold, damp roots — a recipe for root rot.
I was surprised to learn that the University of Arizona recommends that you stop watering cactus when nighttime low temperatures drop below 60℉.
Additionally, it’s advised that you never water cactus or any other succulent (in a container or in the ground) when freezing temperatures are expected. Plants are more likely to suffer freeze damage if they’ve been recently watered, since cells full of water are more likely to burst.
#6 Don’t Water Newly Planted Cactus
You’re probably used to giving a plant a good soaking immediately after transplanting, but that isn’t the best practice with cactus. It’s recommended that you wait a week or two after planting to water. For large new cactus, it’s recommended that you wait a month.
#7 Give Cactus Their Own Zone
Cactus should never be on the same irrigation schedule as the rest of your landscape plants. If you have any that are getting the same amount of water as your shrubs and perennials, plug those emitters today. Cactus can’t tolerate wet roots or being constantly wet at the soil line.
Then either start water manually as needed or create a new irrigation zone just for your succulents. This can be an advanced DIY project or you can hire an irrigation professional.
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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.
