Bentonite Clay in the Organic, Edible Garden

Posted by Bradley Lewis on


Not All Clay is Good

Here in San Diego, we have red clay for soil, and not the good kind! The earth here is predominantly a thick, red clay that makes growing plants difficult at best. Of course, there are some plants that like to grow in clay, but for organic edible gardeners, San Diego clay soil poses a challenge for the following reasons:

  • water runs off
  • only plants suited to the clay soil grow in it
  • it runs in veins 20 – 100 feet wide, mixed with other soils
  • in dry climates (like San Diego where our average annual rainfall is just 9”), clay becomes hardened and nearly impossible to dig

Putting the “arm” in farmer!

In April 2010, after a year of working on my husband, he agreed we could replace the water-thirsty front lawn and put in an organic, edible garden. With the help of volunteers of Victory Gardens San Diego, we proceeded to kill the grass and dig six beds. At times, we (and by we I mean my husband) even had to use a pickaxe to get through that clay. In the fall of 2011, The San Diego Reader wrote a feature article on urban gardening and my husband Kelly and I were included in that. You can read that article online here.

Amending Soil

We amended the soil with gypsum to help break up the clay. Gypsum is technically hydrated calcium sulfate and a soil conditioner. It is inexpensive and readily available at big box home improvement stores and nurseries. We have had very good results with it. Every year when we turn our beds in preparation for spring planting, we place a light layer of gypsum on the bottom of the bed.

Composted Organic Horse Manure

Each season we also amend the soil with organic, composted horse manure. We get ours from Red Worm Products in Escondido, California. Daniel and his wife Laura board horses, raise red worm wigglers, and cut and sell firewood, among other things. We purchase an entire truck bed of organic compost for $25!

Why organic? Because we are going to be EATING the food that grows in our garden. Growing your own food is the BEST way to ensure that you are getting food that is not laden with pesticides or irradiated as well as the freshest.  Their compost is maintained in high temperatures (131°F – 170°F) for at least three days to ensure any harmful pathogens such as E. coli and salmonella are reduced to non-toxic levels. And of course, with proper seasoning (time in this case), the compost does NOT smell like what it is…animal poop!

The Fruits of Our Labor

The magnificent bounty from our garden each season speaks volumes about our soil. Granted, we have the best weather for year-round gardening, but here in San Diego we have the worst soil. We have happy plants because we have rich, organic soil and have worked to break down the clay. If you have issues with *any* type of plant – ornamental or organic – look first at the soil. Make sure the type of soil in the pot is suitable for the plant. Some plants like more acidic conditions, others like soil that is more alkaline.



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