Four Fertilizer Facts & Fallacies for the Southwest

Right around Labor Day is the ideal time to fertilize your landscape in Low and Middle deserts of the Southwest.   I started this topic a few weeks ago on this site, with “Last Fertilizer for the Year.”  That article sparked a four key questions (through my Contact page and on the Facebook page), so here are four answers.

Jargon Alert!

acid = think vinegar and coffee. Acid is in this sense is good.  Muriatic acid is to be wary with.
alkaline = the opposite of acid, think baking soda.
organic matter = compost. Can be bought at a garden center
water holding capacity = soil holds water and releases it to questing roots. The better the soil water holding capacity – the better the growing conditions for your plants.


Can I Use Coffee Grounds?

Coffee grounds can be beneficial for your garden if you live in an area of alkaline soils – like all of the Southwest. In areas of acid soils (back East), coffee grounds should be composted first.

In the Southwest (or elsewhere), if you are going to plant seeds, avoid using coffee grounds unless they are well composted! In a very recent study, it was determined that coffee grounds used directly in the garden soil retard seed germination and slow the growth of young seedlings.


Should I Use Compost Tea?

Compost tea is touted as the solution (pardon the pun) to all your fertilizer needs. While it is easy to make and use, it is simply another form of fertilizer. Here in the Southwest, adding actual compost, not just the tea, is better for your plants in the long run. Adding compost to the soil builds a healthy soil with organic matter and good water holding capacity.


What about Slow-Release Fertilizer?

Unless it is a synthetic chemical fertilizer, all fertilizer releases slowly. The fertilizer sold as “slow-release” is a synthetic fertilizer that has been encapsulated with clay or special polymers so it releases even more slowly over time. This is not the be-all and end-all to your fertilizer needs because it may not offer all of the nutrients that your plants need. Read the label.


Furthermore, most slow-release fertilizers release over six to nine months. Depending on the plant, they may not need that much time.  Bulbs only appear above ground to photosynthesize and absorb nutrients for about three months. A nine-month fertilizer would be a waste of money.

Do I Need a Soil Test?

Many gardening sources tell you to test your soil before you plant plants or purchase fertilizer. A soil test to determine which macronutrients are available in your soil is a great idea if you have any of the following: 1) an agribusiness, 2) you are feeding your family mostly from your land, 3) money burning a hole in your pocket, or 4) a curious nature.


I maintain that the average homeowner does not need a soil test. Two notes about this statement. Note I said “macronutrients.” Most soil tests do not check the micronutrients unless you pay extra. And then, if you simply use a well-rounded fertilizer micronutrients are not an issue. (Macronutrients and micronutrients discussed in Last Fertilizer for the Year.)

The results of any soil test in the Southwest: “Your soil is alkaline.”

Almost all earth life prefers neutral to mildly acidic conditions, so your soil needs added organic matter (compost) to acidify the soil and help the health of all plants. (Yes even succulents like organic matter, it’s part of the reason they start life under trees.) Gardening in containers? You should use new soil media on an annual basis, and so you don’t need a test. If you top-dress your landscape beds with organic mulch (not rock) and regularly apply a well-rounded fertilizer that includes macro-and micro-nutrients – skip the soil test.


If you live in Southeastern Arizona, please come to one of my lectures. Look for me at your local Pima County Library branch, Steam Pump Ranch, Tubac Presidio, Tucson Festival of Books and other venues. After each event I will be signing copies of my books, including, “Month by Month Gardening for Arizona, Nevada, and New Mexico” (Cool Springs Press). Note: this link is to Amazon and if you buy the book there I will get a few pennies.  Better yet – visit your local nursery or botanic garden and buy it there.


© All articles are copyright by Jacqueline A. Soule. All rights reserved. No, no, no, you can’t use the photos.

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2 thoughts on “Four Fertilizer Facts & Fallacies for the Southwest

  1. Hi Doris,

    For Low and Middle Desert: I would give sunburned roses alight trim now, just the badly burned areas.

    Come late January, the whole bush should get the standard annual pruning.

    And thanks for the question! Time for a rose pruning post for the desert.

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