Garden Calendar for May 2021

May Day! Time to get your garden and landscape ready for the summer ahead. Most tasks in May revolve around making sure the water system is working, and fertilizer to encourage fruit production plus warm-season growers to grow.

Irrigation System Tune Up Time

Irrigation systems require checking and tune-up on a regular basis. Some tasks should be done once per month, some should be done quarterly – as the seasons change.

Tune up irrigation system now with these tasks.
* clean filter – knock it out and soak it in white vinegar
* flush out debris – to take off all end caps and run the system to flush out debris.
* check timer settings - change from spring to summer program.

Walk the lines and check the system for leaks or lost emitters (a monthly chore).
Soak your filters in white vinegar to remove calcium buildup. When done add vinegar to water and use it to water your plants.

Fertilizer Tasks

I have several posts on fertilizer in the Southwest, best to start with “Fertilizer 101.”  We do want to help our plants, but in this environment it is easy to over do it.  When in doubt use half-strength and do it again in two weeks.


* Fertilize established Bermuda grass lawns with a high nitrogen fertilizer. Wait at least 2 weeks since last application.
* Fertilize roses every two weeks through bloom period.
* Fertilize deciduous fruit trees (almond, apple, fig, pomegranate, etc) with a fruiting fertilizer any time during the month. Do NOT use too much since it may cause excessive fruit drop. Read and follow label directions.

Chlorosis is easily treated,

* Apply soil acidifier to alkaline-induced chlorosis plants. (More on chlorosis – here)

* After mid-month, fertilize evergreen fruits (citrus, Natal plum, banana, etc.) with a fruiting fertilizer (high in phosphorous). I fertilize on Memorial Day because the next dose is on Labor Day and it’s easier to remember.

* After mid-month, fertilize established palms with a high nitrogen fertilizer. If they are date palms, and you want dates, use a fruiting (high phosphorous) fertilizer instead. I fertilize on these on Memorial Day as well.

No fertilizer for the plants in the Legume or Pea Family, this includes acacia (and it’s kin), Lysiloma (discussed here), Mexican bird of paradise, mesquite (discussed here), Texas ebony, fairy duster, and all the others that make pea-like pods. When in doubt, Wikipedia can help tell you what family a plant is in. Garden nerds like myself are constantly adding horticultural data to the site. Or ask me on the Facebook page, but please post a good picture of both overall plant and leaf close-up.

General Tasks – Anytime in May

* Add color with heat tolerant annuals like sunflower, celosia (cock’s comb), gallardia, and moss rose (the cover photo). More on summer annuals – here.

* Mulch with organic mulches if you haven’t already, especially citrus and vegetables.

* Plant hot season vegetables and herbs, including: amaranth, muskmelon, okra, pepper, squash, tomato, basil, marjoram, oregano, and rosemary. More on warm season vegetables – here.

* Plant or transplant cacti and other succulents, such as agaves and hesperaloe – try to do this before the 100’s hit.

* Blast spider mites off evergreens with water or spray with insecticidal soap. Repeat as needed at least every other day for 10 days until mite population is knocked back.

* Remove spent flowers (deadhead) to prolong bloom on roses and annuals.


After mid- May

* Harvest any ready onions, shallots, and garlic.

* Watch for caterpillars and treat with insecticidal soap. Problems are grape-leaf skeletonizers on grapes, skeletonizers on Texas mountain laurel, and orange dogs on citrus (these you can pluck off).


Hey – don’t forget to be careful out there!

Remember the 3H’s for safety – Hat! Hydrate! Hands!

Peace, Jacqueline

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More about overall care of your land and landscape in this book: Month by Month Gardening for Arizona, Nevada, and New Mexico (Cool Springs Press).  This link is to Amazon and if you buy the book there the Horticulture Therapy non-profit Tierra del Sol Institute will get a few pennies – at no extra cost to you.

© 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.

Cover photo: Portulaca Margarita Rosita. Photo courtesy of AAS.

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