Water for Plants – Part I

July is nigh, and since July is “National Smart Irrigation Month” let’s look at just what it takes to be smart about watering your plants in the Southwest.

All plants need more water as temperatures rise and it becomes harder to cool themselves.    Water is critical in our region, but don’t let your plants become daily “drip sip” junkies.

drip irrigation emitter with a single drip

“Drip-sip Junkies?”

Many homeowners leave their irrigation controllers to factory set defaults. This runs the irrigation system for 20 minutes per day. A scant 20 minutes barely wets the area around the drip emitters and thus the plants just keep growing their water absorbing roots right near the emitters. They do not spread out and grow strong anchoring roots. They do not reach deeply for the water far below the hot surface of the soil. They just hang out by the emitters, waiting for their daily “fix” – that little sip of water.

Water with a hose? You may still be creating drip junkies. Do you go out after work and stand by the plants with a hose for 5 minutes? Indeed, that is even worse because plants don’t use the water as the sun is going down. You just lose the water to evaporation overnight.

water hose spouting water

Water Deep and Long

Instead of a “sip” of water every single day, provide ample water every three days or more. My established plants get water once a week, and it would be even less if I had monthly timers.

In short – apply water less often BUT for a longer time, so the water sinks in two or even three feet into the ground – where roots should be growing.    Roots need to encouraged to grow deep underground where it is cooler.  Grass roots in the prairies reach over 12 feet deep. Mesquite roots have been shown to grow more than 300 feet deep.


Deep and Wide for Anchors

Irrigate out at the dashed line – this encourages roots to spread wide and anchor the tree

Trees need to be encouraged to anchor themselves well, so apply their water well away from the trunk.  This encourages wide anchoring roots.

Worried about your walls? This gets back to watering deeply. Send those roots deep after the water they need and your walls should be just fine.

Deep roots naturally occur in many species. Exceptions abound of course! The non-native mesquites are one prime example, they will heave your driveway given half a chance. Arizona ash (native to river areas) is another that will crack your sidewalks. Little leaf elm is insidious. Some mulberry species are shallow rooted as well. Use my search bar (on the side near the top) for some nice tree ideas.

Water Wide

You may need to move your drip emitters. You may need to add drip emitters. You plants are not the tiny little nursery pets they were when the irrigation system was first placed. Just like babies, they grew larger. Just like kids, they need new “clothing” every so often.

When to Watergardening with soule photo of fungus that grow when you water lawn at night

Water at dawn to conserve water. This will also discourage fungus growth (they love night-time water). Water at dawn to give plants the water they need as they “wake up” for the new day.

Plants only need water when they are photosynthesizing. In summer this is in early morning.    After about 9 am in summer they generally close down active photosynthesis for most of the day, and just survive the heat.

gardening with soule photo illustrating normal wilt to conserve water
The drooping leaves on these cucumber plants are in passive, “conserve water” mode for the day. They are not wilted, they have their leaves curled to help reduce excessive water loss.

This “water at dawn” concept means that you will have to change the irrigation timers every so often.  Quarterly is good enough.  It also means that if you try to spray for weeds once plants are shut down for the day – it is not very effective.

soule-garden-successPlant Nerd Note

When I say “plants” I mean C-3 and C-4 photosynthetic plants. CAM (Crassulean Acid Metabolism) plants do things slightly differently.    For all of these, watering at dawn  is still a good idea. If you have no idea what I am talking about – I did say it is a nerd note.

Don’t Kill With “Cold Turkey”

Continuing the “junkie” idea – you can’t just switch how you water from one day to the next – and expect your plants to survive. Water absorbing roots can grow quickly – but not that fast. Instead – taper off! Start first with a good hour soak, and then skip a day. Repeat this for 2 to 3 weeks, then switch to water every third day. This is short term pain – for long term gain!

gardening with soule photo of landscape with smart irrigation

What You Gain with Smart Irrigation

Long but deep water means less water lost to evaporation ($$$). It also means that the salts and calcium in our water do not start accumulating in the soil, harming or killing plants ($$). Plants reaching far for water will naturally find the minerals they need for life, and thus need less fertilizer ($$). Deep rooted trees are unlikely to fall over in summer storms – possibly harming your home ($$S$!).

Question – How do You Measure Success?

I am here ,,, “to help you succeed with your garden goals.”

Please do share those goals with me! If you have questions, ask them in the comment section on any post, in a response to any newsletter, or on my Facebook. My Instagram was hacked and I have lost access to that platform. You can also find me as GardeningwithSoule on Tiktok.

More on irrigation in my Month by Month guide

More About Irrigation and Watering in this Book:

May I recommend my book?  The Month By Month Guide offers tips for your landscape (yes even lawns and roses) in every month of the year.  I have a few copies left and am offering them to you – my loyal readers. Price is what you would pay on Amazon – only when you buy from me you get a signed copy!soule-books-buy

From the review:

“A great reference book is key to successful gardening in the region where you live. Arizona, Nevada & New Mexico Month-by-Month Gardening takes the guesswork out of gardening for anyone residing in the Southwest. With this book, you’ll know what to do each month to enjoy a thriving garden all year, from January to December. Chronologically organized, this guide is full of critical gardening when-to and how-to advice, along with illustrated step-by-step instructions.

The book’s author is Jacqueline Soule, a Tucson-based gardening expert. She knows this arid region inside and out, and she’s written several articles and books packed with her gardening advice. Arizona, Nevada & New Mexico Month-by-Month Gardening showcases Soule’s expertise in one easy-to-read guide.”

Profits from the sale of this book go to the Horticulture Therapy non-profit Tierra del Sol Institute.

Cover image = summer blooming rain lilies. 


© Article copyright Jacqueline A. Soule. All rights reserved. You must ask permission to republish an entire blog post or article. Okay to use a short excerpt – but you must give proper credit to Gardening With Soule. You must include a link to the original post on our site. No stealing photos.

One thought on “Water for Plants – Part I

  1. Great advice on watering in the AM. I had always thought it was better to water in the evening so we could soak in overnight, but it just seem to attract the javelinas to root around and dig up my irrigation lines.

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