BORAX as Fertilizer and Soil Amendment



Borax is a naturally occurring mineral salt.


Why might borax be good for the garden?

Borax is related to the mineral boron, which supports healthy growth of cell walls and membranes.

Where can I find borax?

Borax is most commonly mined from dried up lakes. Here I am in all my splendor hunting for salt crystals in a slimy wine-colored, brine pool. We also found several clumps of borax on this trip to Searles Lake, California.

According to the Historical Society, mules started hauling borax to the newly extended railroad system in the 1870’s. That area also produced potash and sodium sulfate until 1996 when all production was shut down after 81 years!

Where to find borax


Although it’s fun to search for borax “rocks” out in “no-where-land”, you can save yourself the long drive, scorching heat and dusty air, and pick up some powdered borax from the grocery store. 20 Mule Team Boraxâ is a laundry booster product containing one of the several varieties of boron chemical compounds: sodium tetraborate.Using store bought borax

Which plants may benefit from borax?

Many plants are sensitive to a boron deficiency. Cauliflower and celery seem to need more than what is naturally available in most soils. If you grow celery and find that the ribs have brown streaks then you might need to add some boron. Beets get black spots when they can’t get the boron they need. Broccoli, cabbage kale, kohlrabi and mustard greens are also candidates.

Combine borax with…

Let’s start with a warning. Some of the same plants that crave lots of nitrogen also need adequate boron. But there’s a catch. Boron can become less available to plants when there is too much nitrogen. Therefore, I recommend you not use synthetic nitrogen fertilizers on soil where boron-friendly plants are grown. The laboratory-created nitrogen is too concentrated, releases too quickly, and has the potential of throwing off boron uptake.

Use a small amount of alfalfa or fish fertilizer along with the borax to gradually supply nitrogen to your plants over a few weeks. It is convenient that the timing for both nitrogen and boron applications is early in the growth cycle.

Other options include any of the fertilizers that offer trace minerals such as kelp and borage.

Borax Fertilizer Recipe

For an area about 2 square feet: Mix only ½ teaspoon of borax into one gallon of water. You can add it straight into your watering can. Water the plants and soil around your plants with this solution. Wait two weeks and apply it one more time.

For an area of approximately 3 square feet: Mix ½ tablespoon of borax into 3 gallons of water. Water the plants and soil around your plants with this solution.

The best time to apply the liquid fertilizer is in the morning and the best stage to apply is early to halfway through the growth cycle, a month before cabbage heads or kohlrabi bulbs form.

Do Not Overuse Borax!

A few weeks before publishing the book I read a forum post where a lady dumped an entire box of laundry borax into her raised garden bed next to the broccoli, cabbage and cauliflower. Everything died and her soil is ruined for an unknown period of time.

Borax Quick Tips

  • Remember that you must use borax (sodium tetraborate), NOT boric acid!
  • Borax is also great for sunflowers. Use the first recipe that calls for just a gallon of water. Apply the borax solution a month before flowers begin to bloom and then again two weeks later.
  • If you don’t have borax around, you can amend with compost to improve your chances of adequate amounts of boron. The University of Wisconsin published a paper about “Soil and Applied Boron” and it mentioned how boron deficiencies usually occur in soils that have pH ratings at 7.0 and above. As explained earlier, compost can help keep our pH to a healthy range between 6.0 and 7.0.