I had my soil tested and I’ve fixed my fixable problems. It’s clay heavy, which I can’t do much about, and supposedly critically short on boron.

How do you add boron?

Maybe 20 Mule Team Borax if it’s still made. I remember reading this long ago. Others here will know more.

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I’m hoping someone will chime in and describe how much to use as it is an important requirement but is toxic in high doses. Would a teaspoon or a tablespoon amount suffice?

I think a teaspoon will probablysuffice, per tree. But going by soil test recs is helpful and a boron test with specific guidelines is not expensive. Hambone is correct about a good homeowners source.


You can also order 100% pure boric acid online. For the usage here is some guideline:

From the source:

While borax in large doses kills unwanted plants, in small doses it can be a soil booster – especially in sandy soils that may be mineral deficient. A large vegetable garden of 1,000 square feet can safely benefit from 6 to 7 tablespoons of borax mixed in at tilling, either directly or diluted in water. Fruit trees – such as apples – benefit from the effects of borax, which not only fertilizes but can assist in fighting off rot and fruit-pitting.


I use Borax too on occasion at about the level Alan mentioned, but it may be helpful to all of us if you could contact the folks who did the test and get a recommendation from them,. If you are ‘critically’ short, the teaspoon my not be enough, and they may have another form they recommend. Let us know.


I use borax (20 mule team) in my yard to fight back the creeping Charlie. I’d have good control, too, if it were not for my neighbor’s yards maintaining a healthy population. I walk around and sprinkle liberally, perhaps a cup per 15-20 square feet.

Additionally, research is showing that regions with abundant naturally occurring boron within the soils also seem to correlate to reduced arthritis among people who consume vegetables grown in that soil. However, too much is quite toxic to plants, as is true for many things. When sprinkling I’ve spilled more than I wanted a couple times and burned the surrounding grass.

(I actually had a case of magnesium toxicity show up in a couple of my plants last year, especially a clematis whose foliage and blooms were badly misshapened…)


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The report showed boron at less than .1 ppm, which was at the bottom side of the ‘very low’ category. I was hoping to not buy a big box of 40 mule team for my 150 sq ft garden since I seem to need a few tablespoons at most. The listed application was .06 lbs of borax per 1000 sq ft.

Mule team borax costs under $4.00 here.

I use it for a few things around the house anyway. My box from 3 years ago is still half filled, at least.


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It’s a good laundry additive!


Sodium tetraborate, irrc. Also used in a few photographic developers. It’s mined from nearly pure natural deposits in the southwest, I think.

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Here is a quick read about boron re: plant deficiencies. 20 Mule Team is pure borax but that is only about 11% boron. I might get a box 'cuz, like it has been noted, it’s good for laundry and general cleaning, too, and cheap. When my rescue apple tree really put out some apples some of them suffered from water-core; and my new pear shoots had some die-back; both of these conditions could be related to lack of boron (see symptom chart). The apple tree is now basically in the woods so competition for nutrients is fierce.


Which is plenty! Most fruiting plants require Boron for health but there are limits.

[corrected per Olpea’s remarks below]

  • 20 Mule Team Borax (refined for purity) has a density of 1.73 g/cm^3.
  • Borax is 11.339% Boron by weight, so that’s about 0.196 g/cm^3.
  • There’s about 4.93 cm^3 per teaspoon or nearly 1000 milligrams Boron (net) per teaspoon of Borax.

Notice that Borax is a Sodium compound Na2[B4O5(OH)4]·8H2O. Knowledge of existing Sodium in your soil should be taken into account before application because it can be an acute plant toxin.


Like others, I’ve used 20 mule to fertilize. Generally bringing the boron up to 1 ppm is good enough for most crops. 3ppm is too much, which demonstrates the very fine line of this trace mineral.

I calculated the amount differently. A foot acre of dry soil weighs about 3 million pounds here. So adding 3 pounds of actual boron per acre will bring the soil boron up by 1 ppm. That’s adding roughly 30 lbs. of Borax per acre.

A 150 sq.ft garden is about one 300th of an acre. If my math is right, that translates to 0.1 lbs of Borax for a 150 sq.ft plot (or about an ounce and a half).


I read that paragraph a couple times and still don’t understand what you’re trying to communicate. 20 to 50 mg per kilogram of soil is the same as 20 to 50 ppm of boron in soil by weight. From recommendations I’ve seen, that’s off by a factor of more than 10.

Are you sure you aren’t referring to leaf analysis? For leaf analysis, I’ve seen values in the 20 to 40 ppm range for peaches.

1 teaspoon of Borax per 110 lbs. of soil (i.e. cubic foot of soil) would be way too much.

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A teaspoon of purified Borax weighs 0.3 ounces, so you are recommending 5 [corrected] times alan’s dosage per tree in a 10’ x 15’ area?

I think an important factor in looking at recomendations is annual rainfall. Our salts wash out yearly - good and bad. That factor may be taken into account in some areas, whereas in dry areas buildup can occur.

@Chills Scott,

Borax kills creeping charlie? Great news. I tried many chemicals to kill it, nothing work. Unfortunately, they grown right in the middle of grass/lawn and is about to take over the lawn.

No Richard, that’s incorrect. I recommended 0.1 pounds for the 150 sq.ft. area, which translates to 1.6 ounces (or 1.6 ounces per 150 cubic feet) since for most crops, guidelines are for the first foot of topsoil, since that’s all you can fertilize (practically speaking ). I’m on my phone so I can’t offer links, but boron recommendations are around 2ppm for peaches.

I’m not trying to challenge you in some big way. I just didn’t want someone poisoning their land by your misstatement of the numbers. We all get our facts wrong occasionally, I know I do.

Anne, you are absolutely correct nutrients wash out of the soil based on rainfall and soil composition. It’s always a good idea to have soil tests done periodically, so there is much less guesswork. That said, it’s been a while since I’ve had one done. I need to follow my own advice!


Yes, although Boron can be very resilient when introduced to clay soils such as TheGrog’s. On the flip side – it can also be difficult for plants to uptake in clay.

I agree with your assessment that 1 tsp per cu.ft. is too much, but I’m also concerned about 5 tsp [corrected] of Borax per tree – esp. the quantity of Sodium salts it would impart on soils.

For my trees I use a water-soluble sodium-free compound that is 0.02% Boron by weight. In a typical dosage this results in about 0.2 ppm Boron in water.

I read about boron deficiency on strawberries, which described mine, several years back, so I bought some 20 Mule Team and sprinkled that lightly, plus the usual 10-10-10 on in mid-summer. The leaves turned brown, dead, and crunchy. Then they grew new leaves in lush bushes a foot tall! The next year I had a huge bumper crop. They have gradually gone downhill, so probably need it again, but we are still eating berries from the freezer from a couple years ago. Last summer I decided to try sprinkle about a teaspoonful of it around each of my 5-10 year-old fruit trees and blueberry bushes, since they are planted in sand and not bearing well. We will see if we finally get any cherries or plums this year.