Connecting Greater Phoenix gardeners with information that helps put xeriscape principles into action.

Gardening Tip: What Kind of Fertilizer Should I Use? (Part 4)

Earthway Fertilizer SpreaderOK, so…you now know a little bit about fertilizers.  You’ve mastered N-P-K values and types of fertilizers.  And you have pretty good idea which fertilizers to choose.  The last piece of the puzzle is knowing how to apply them…and when.

The most important thing about applying fertilizer is to read the label and follow the directions.

The next most important thing is to appreciate that we live in the Phoenix desert where temperatures soar to a soul-scorching 110 degrees or more in the summer and the risk of fertilizer burn is high.  It’s a conundrum, I know…fertilizers can burn so we should apply them at the hottest time of the year.  Right.

But the truth is that using fertilizers inappropriately can cause plants to burn.  So here’s the best way to apply fertilizer:

  1. Thoroughly water the area you want to fertilize.
  2. The next day, apply your fertilizer in the late afternoon or early evening…especially in the summer.
  3. Immediately follow that application with another thorough watering.

How you apply them will be driven by the product itself and the label directions.  I use this same Earthway spreader to apply fertilizer pellets to our lawn.  It’s sturdier and much more reliable than anything I’ve ever purchased at a big box store.  For liquid fertilizers, I dilute them in a garden sprayer and spray both the soil and the foliage.

(Quick note:  Spraying the foliage quickly sends fertilizer down the shoots into the roots.  But unless you’re highly skilled or have a highly controlled environment, don’t spray foliage when it’s more than 90 degrees outside.)

Now, there may be a temptation to overfertilize.  I mean, hey…that plant has never looked better, so give it more…right?  But overfertilizing stresses the plant, making it much more susceptible to diseases and pests.  It’s kinda like using Recombinant Bovine Growth Hormone (rBGH) in cows.  They’ll produce more milk, yes, but it puts both the cows and humans at greater risk for adverse health effects.

Finally…WHEN should  you fertilize?  Well, after forgetting what I’d fertilized and when, I put together a quick chart to remind myself.  I then turned it into a handy quick reference fertilizer guide for January-June and a quick reference fertilizer guide for July-December.


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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Gardening Tip: What Kind of Fertilizer Should I Use? (Part 2)

N-P-K Values on a Fertilizer LabelIn my last post, I shared a little bit about what fertilizer is.  Here, I’ll de-mystify those little numbers on the package!

Nitrogen (N), phosphorus (P), and potassium (K) are the three primary nutrients in fertilizer.  Manufacturers use N-P-K values to show the percentage of each of those nutrients in their products.  For example, 21-7-14 indicates that you’re getting a product that contains 21% nitrogen, 7% phosphorus, and 14% potassium.  In a 100 lb. bag, that would mean 21 lbs. of nitrogen, 7 lbs. of phosphorus, and 14 lbs. of potassium.

Getting down into the dirt, nitrogen helps produce that lush green foliage that we love, while phosphorus helps with root growth and fruiting/flowering.  And potassium helps with overall plant health and disease resistance.

Now, that’s pretty cool, right?  But you’re probably wondering what the other 58% is.  Truth is, with organic fertilizers, the rest is some combination of secondary nutrients like magnesium, sulfur, and calcium along with some trace nutrients.  Fillers and other ingredients that help with application and absorption make up the remainder of most inorganic fertilizers.

A 21-7-14 fertilizer (which is what I use on my bermudagrass) is what’s known as a complete fertilizer because it has all three primary nutrients.  An incomplete fertilizer lacks at least one of the primary nutrients and, therefore, would have a zero value…for example, 1-11-0 is an incomplete fertilizer because it does not contain potassium.

Now comes the fun part:  organic and inorganic fertilizers.

Organic fertilizers, as you can probably guess, are made from the by-products of living things. They can be either naturally made or manmade, but they almost always contain carbon.  Compost is a naturally occurring complete fertilizer made from yard and kitchen waste.  If you use compost, you will probably not have to use any other fertilizers.

Other organic fertilizers include blood meal, bone meal, alfalfa, coffee grounds (yes!), fish emulsion, liquid seaweed, guano, and some others.  While they can be expensive and slower to absorb, these fertilizers often require fewer applications, contain beneficial trace nutrients, unleash bacteria that the soil loves, and improve the soil.

Inorganic or synthetic fertilizers are cheaper, absorb more quickly, and contain more super-charged nutrient levels.  But it’s also easier to go overboard with these guys, resulting in deliriously happy, but disease-susceptible plants and fertilizer burn.

So…which is the best one to use?  Hint:  Our native and desert-adapted xeriscape plants in our Phoenix desert gardens generally make their own nitrogen.  Look for part 3, how to choose fertilizers, coming next!


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