How long and how often should you be watering your trees and shrubs in the summertime if you live in the desert? The answer may surprise you.
By far and away, the most common issue that I run into at the nursery has to do with watering. On a daily basis, people bring in leaf samples that are scorched along the edges or they complain that their plants are simply not thriving. “What’s your watering schedule?” is generally the first question I ask, which often brings us to the core issue pretty quickly.
Almost without fail, the answer that I get to this question is somewhere along the lines of “Five minutes, three times a day,” or “Fifteen minutes, twice a day.” The problem is that if you’re watering with drip emitters, this type of schedule can’t possible deliver the amount of water that your trees and shrubs need in order to survive. In fact, this kind of watering could very well be the fastest way to shorten the lifespan of your landscaping plants.
Why is everybody watering their plants incorrectly?
Sorry, Southern Nevada Water Authority, but you’re getting called out on this one. While our regional water conservator has done a great job of helping local businesses and residents reduce their water usage over the past decade, they’ve also managed to confuse the hell out of a lot of people at the same time. Let’s take a look at the watering schedule that the SNWA sends out to let you know how to run your irrigation throughout the year…
Pretty clear, right? The vast majority of people that I talk to can tell you right off the bat which group their home is in. The only problem is that this schedule refers to lawns only and it has nothing at all to do with how you should be watering trees and shrubs. Look down there at the very bottom, in red, where it says “Run sprinklers 3 times, 4 minutes per cycle on your assigned day(s). For drip systems, see inside.” Don’t feel bad if you never noticed it before. Nobody else has either.
Better yet, the SNWA runs commercials at the beginning of the summer announcing “It’s time to change your clocks to seven days a week!” Again, they are only talking about your grass sprinklers, so if you don’t have a lawn, they aren’t talking to you.
If you want to know how you can save money on your grass watering bill, take a look at this post.
Unfortunately, neither the printed schedule nor the commercials make it clear enough that daily watering in the summertime is only appropriate for lawns, so there are countless desert residents who dutifully change their clocks to seven days a week and wind up doing more harm than good to their trees and shrubs. There are even homeowners’ associations and landscaping companies around town that erroneously set drip irrigation timers following this schedule.
What is appropriate watering for trees and shrubs if you’re using drip irrigation?
Now’s the part where I’m going to tell you how you should be running your drippers and then you’ll stare at your computer screen in complete and utter disbelief. I know this because I’ve been having this talk with people for years now and I get that look every single day. Bear with me though and I’ll explain why this type of watering benefits your trees and shrubs in the long run.
In the summertime, which is roughly May through September in Las Vegas, your drip emitters should be running for one hour, one time a day, but only three days a week. I know, your mind is blown. Go ahead, reread that sentence as many times as you need to in order to process it. One hour, one time a day, three days a week. Not every day. Not two or three times a day and absolutely, positively not for five or ten or twenty minutes.
Why you should be running your drippers for more time, less often…
First and foremost, drip emitters are not rated in gallons of water per minute, like lawn sprinklers are. Instead, drippers are described in gallons of water per hour. The most common dripper is probably a 2gph emitter, which means that if you run it for a full hour, your plant will get 2 gallons of water from it. Run it for fifteen minutes and it will only put out a half gallon of water. Five minutes means that your plant is trying to survive on a Dixie cup of water in the Mojave Desert.
But wait, you’re thinking, I run my drippers three times a day for ten minutes, so my plant’s getting a full gallon of water by the end of it. That should be plenty of water, right? Sorry, that’s not how it works. Basically, you’re just wetting down the top of the soil over and over again and your plants aren’t getting water down deep where they need it. Aside from that, one gallon of water isn’t enough for virtually any tree or shrub to survive on when it’s been planted in a full blast of desert sun.
By running your drippers for one solid hour, preferably in the morning, you send the water down deep, which prompts the roots of the plant to go deep after it. This not only establishes a deep-rooted plant, which is always a healthier plant, but it also sends the roots to a depth in the soil that is a more consistent temperature year-round, so it’s less susceptible to both the heat and the cold. Then, on the days between waterings, the top layer of soil is allowed to dry out slightly, allowing oxygen to reach the roots. Plants breathe, just like you and I do, and they can’t do it if the soil is wet on top all the time. Another benefit to deep watering your trees and shrubs is that it helps you to avoid those vicious surface roots that can cause serious damage to your foundation, driveways, walkways and patio.
Worried about running afoul of the SNWA?
Don’t worry, you won’t be. As long as you aren’t running your drippers between the hours of 11 a.m. and 7 p.m., the SNWA has no problem with you at all. In fact, this is precisely the type of watering that the agency recommends for your landscape in the section of their schedule titled “Drip Tips for Plants.”
If you can get the watering straight, you’ll be amazed at the plants that you can get to grow and thrive in the Mojave Desert. Just remember, longer, slower, less frequent watering is better for both your desert garden and your water bill.