Summer Watering for Trees and Shrubs in Las Vegas

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.

 

Image courtesy of Scott Nelson via Flickr

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…

 

SNWA Lawn
Image courtesy of Southern Nevada Water Authority

 

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.”

Image courtesy of Southern Nevada Water Authority
Image courtesy of Southern Nevada Water Authority

 

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.

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17 Comments

  • Hi!! I water my plants with a hose turned on very low to allow for a slow drip. Should I water my plants for 1 hour like you suggest doing with drip emmiters but with the hose? Thanks in advance!

    • You sure can, Holly. Just be sure to set a timer so you don’t forget. Thank you for the feedback and for being so patient with my response. I’ll be posting new material soon and I hope you’ll check back 🙂

  • Are my shrubs with tips of leaves turning Brown being overwatered or burning????
    Getting 2 different responses…
    I never remember my dad covering the trees and shrubs for protection…
    My husband waters by hand since our Rainbird broke…AND he does NOT slow drip!
    This is a constant battle…I slow drip
    Thanks so much….
    Please advise…
    I have another question, but I don’t want to overwhelm you….ha ha

    LAS VEGAS resident 55 years

    • Hi Charisse,
      I’m sorry for the delayed response but fall really is second spring in the desert and my calendar’s been pretty crazy. Brown, crispy leaves on a plant are usually indicative of saltburn, not overwatering. It goes back to giving your plants long, slow drinks of water to flush the minerals in our soil away from the roots of the plant as much as you can. Short, frequent watering draws the minerals up to the top layers of soil and into the roots of the plant. What you’re seeing is the plant trying to get the excess minerals out of its system basically. Some plants are much more susceptible to this than others which is why you want to look for plants that can tolerate our alkaline soil. I hope this helps! Questions are always welcome here, I just ask for patience with the answer 🙂

  • We bought a house in Summerlin last October and the yard “HAD” 7 Italian cypress trees. 2 of them have been removed because they died now the rest of them are starting to turn brown. We had a company come out and treat them for Boars and such. The drip emitters were not working so we had those fixed and I can nit seem to find anyone’s who knows how often and how long they should be watered. I have googled, asked local nurseries and everyone gives me a different answer. I do not want to lose the rest of these beautiful trees, they are mature and at least 30ft in height.
    The drip irrigation is all on 1 timer. PLEASE HELP ME SAVE THEM 🙏

    • Hi Laurie, congrats on the new house and humongous puppy. I’m sorry to hear the cypress are looking so bad. If they’ve been treated for borers the treatment would likely have taken care of dust mites, which are another common Cypress pest but it’s hard to know for sure without knowing what chemical was used on them. If you’re watering for one hour three times a week right now then you’re right on track. That can be switched to 6 days a week during the summer months for the Cypress.

      Just as a heads up, if the trees were planted right next to a wall those dust mites will probably be an ongoing issue for you. When dust collects in the branches up against the wall the mites move in and suck the moisture out of your tree causing ugly brown blotches that will eventually move all the way up the tree and from one tree to another if they’re near one another.

      I hope this info helps and that you’re able to save your trees. Please feel free to ask away if you have any further questions! Thank you for reading 🙂

  • Thank you so much for your help! . I have set the drip system for 1hr Tuesday/Thursday/Saturday
    Hopefully the rest of the shrubs, plants and palms will be happy with that setting. I moved here from North Idaho and thought I had a green thumb until I moved here…….. 🙁

  • Hi, thanks for all the great tips. I have 2 beautiful monk vitex trees, very tall and wide. They look more like trees than bushes. This year the branches do not have the lush green leaves and bright purple cone flowers as in previous years. The branches are sparse and and are mostly dead twigs with sparse leaves and just a few flowers. I have read this tree does not like much water. It has only 2 drip irrigation near the trunk. If i set the rest of the plants in my backyard for watering 1 hour three times a week, will that help or hurt this tree. I love the natural shape of this tree and it is too big to prune anyway. Also What is the best plant food for a purple vitex tree? Thanks so much!

    • Hi NL,
      Thank you for the question. Vitex are a fairly drought-tolerant tree but they’re not anywhere as tolerant of low water conditions of true desert trees like mesquites, Acacias and desert willows. They also benefit from a good pruning once a year to thin out dead wood and crossing branches. This is true of any tree really but the Vitex especially so. You’ll want to expand the wetting pattern under the tree as far out as the canopy goes and you can pull back the emitters near the trunk. The pattern should start about 1′-2′ from the trunk and there should be an emitter roughly every 3′ around the tree. You could also just go out there and soak it with the hose every so often (a couple of times a week during the summer heat) and it should flush out with some new growth. The dead wood will still need to be cleaned out though and I can’t recommend highly enough that you hire a Certified Arborist to do the work. Cutting into living things with a minimum of damage really is a skill 🙂

  • Great tip and article!. ill change my system right away, this is my setting for my front yard and everything looks great. Just curious about fruit trees in pots, at 20 mins its already leeching water underneath the pots, should i let it leech and still give the ones in pots an hr of drip irrigation?

    • Thanks, Ben! For the fruit trees in pots, it’s good to see water coming out the hole in the bottom of the container since that means you’re soaking it thoroughly. If you’re seeing a lot of water it could be that the emitters are putting out too much water or the roots of the tree are taking up so much space in the pot there’s not enough soil to really hold much water. The rootbound situation will normally happen when the tree has been in the same container for years so if they’re newly planted, I wouldn’t be worried about it. A fruit tree in a pot in plenty of sun here in Vegas will be kind of tough to overwater though so if it’s looking happy and producing plenty of juicy fruit for you, it sounds like you’re doing something right. Good luck!

  • Hi! I’ve read your article and it all makes sense! I do have a couple of questions. We just planted pigmy date palms in May. I have been watering them morning and evening. Is once a day (or even less) ok with newly planted palms? I also have just planted smaller plants that I have been watering morning and night. Should I reduce to just one or the other? My Mexican Bird of Paradise is struggling and I’m not sure what I’m doing wrong! I see them all over town in the scorching heat and they are big and beautiful… mine seem to be losing leaves and dying! Please help!! Thank you!!

    • Hi Kresha, thank you for reading my blog. Watering daily isn’t a problem for new plants in the summer heat but it’s best to stick to one deep soak in the morning for most plants. That could be the problem with your bird-of-paradise since they hate staying wet all the time. Your pygmy palm may struggle here in a hot spot regardless of its water though; Vegas full sun can fry their fronds in no time. If you have small plants in pots they may require extra water but 2x a day still seems like a lot unless they’re in a blast of sun maybe. Otherwise, give ’em a good soak in the morning and they should be just fine. Good luck!

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