Gardening Tip: What Kind of Fertilizer Should I Use? (Part 3)

Results of 1942 Fertilizer DemonstrationIn a previous post about the importance of fertilizing, I mentioned that native and desert-adapted xeriscape plants produce their own nitrogen or have otherwise adapted to our Phoenix desert soils.  So the soil that they grow in requires no fertilizer.  Then I talked more about N-P-K values and inorganic vs. organic fertilizers.  So now…how do you choose the best fertilizer for your Phoenix desert garden?

First, let me say that when it comes to edibles — whether vegetables, fruits, or nuts — an organic fertilizer is always recommended.  I mean, you’re growing your own to get that farm-fresh taste, right?  So why ruin it by adding in the same stuff that the mass producers use to get blemish-free, nearly perfect, fast-growing, long-lasting tasteless specimens with some potentially unhealthy side benefits?

(By the way, deciding whether to use organic or inorganic fertilizer is simply a matter of personal preference.  I tend to go organic as much as possible, but some things do not respond well to organic methods.  Take killing off Bermudagrass, for example…)

That said, which organic fertilizer is best?  If you have or can get compost, that’s your best option.  It’s a complete fertilizer that adds a layer of slow-released goodness to the soil that just can’t be beat.  Fish emulsion, liquid seaweed, alfalfa meal, coffee grounds (wish I drank the stuff!), and guano are also complete fertilizers that work well.  I primarily use fish emulsion and compost, but I understand that liquid seaweed provides a little heat resistance in the summer.

If your soil just needs a boost of nitrogen (no phosphorus or potassium), try blood meal.  If it needs a shot of phosphorus (no nitrogen or potassium), use either rock phosphate or bone meal.  If it’s potassium your soil needs, stick with liquid seaweed.  Remember, though, that, unless you have a specific soil issue, using these incomplete fertilizers may require you to also add in the missing nutrients.

As for inorganic fertilizers, look for a locally manufactured product — not only because it’s good to support our local businesses, but because these guys know our soils better than any national brand can.  You can also use these products as directed.  With national brands, you may have to make some quick calculations to get the right “dose.”

Here are some quick fertilizer recommendations:

  • Citrus – Requires lots of nitrogen, so look for a complete organic fertilizer that has lots of nitrogen and smaller amounts of phosphorus and potassium.
  • Roses –  Likes lots of nitrogen and phosphorus, so try a complete organic or inorganic fertilizer with lots of nitrogen and phosphorus and a small amount of potassium.
  • Bermudagrass – Use 21-7-14 (or something with a 3-1-2 ratio) inorganic fertilizer or a thick layer of compost. (Read the article Turf’s Up:  Growing Healthy Lawns in Phoenix Desert Landscapes for more information.)
  • Container plants – Container plants lose nutrients every time they’re watered, so all container plants require monthly feedings. For edibles, choose a complete organic fertilizer.  For other plants, choose a balanced 10-10-10 or similar organic or inorganic fertilizer.  For cacti and succulents, use a 50% dilution of a balanced 10-10-10 fertilizer.

Keep in mind that these are general guidelines for otherwise healthy Phoenix desert soils.  Two nutrient deficiencies commonly found in our desert soils will require specialized treatments:  zinc (occurring most often with corn, beans, pecans, and grapes) and iron (found mostly with turfgrass, citrus, apples, peaches, and some other ornamental plants).

A final note:  many gardeners use chicken or cow manure to organically fertilize their soils.  Done right, it’s entirely safe and just as nutritious as other organic options.  But I personally think it’s gross so I don’t use it on  my edibles.  I do use it twice a year on my lawn.

So…now that you know which fertilizer to choose, how do you apply it…and when?  Part 4 covers these burning questions…and offers a handy quick reference fertilizer chart for January-June as well as a quick reference fertilizer chart for July-December.  Stay tuned…



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