Episode Details

The conversation started innocently enough. Penny Pawl, Napa County (CA) Master Gardener, was chatting with me about soldier flies: ominous-looking, wasp-like creatures who, along with their grubby larvae, might be populating your worm bin or composting bin. You can listen to what she had to say about that in Episode 214 of the Garden Basics with Farmer Fred podcast.

Or, read a previous edition (July 1, 2022) of the “Beyond Garden Basics” newsletter where we talked in depth with Sacramento County Master Gardener Susan Muckey about her take on soldier flies.

My chat with Pawl then veered into the worm bins that she uses on her property. The collection, she said, included four African Keyhole Gardens, with worm bins. What??? My ears perked up. And we were off to the races!

Penny Pawl is certainly a very inquisitive gardener. When she heard about the African Keyhole gardening method, she had to try it for herself. And as you heard in today’s newsletter podcast, hers are a roaring success. So much so, she now teaches classes in African Keyhole Gardens in Napa County.

So, what is the history of African Keyhole gardens? Pawl explained them in a column for the Napa County Master Gardeners, entitled “African Keyhole Garden - Great Garden Idea.”

“A so-called keyhole garden bed has a dead end opposite the opening. At the dead end is a compost bin. More than 20,000 of these have been built in Africa.

The Texas Master Gardener Association has held a number of workshops to promote this type of garden. There are also standardized plans. Their version is a six-foot-wide garden bed with a twelve-inch-wide bin made of chicken wire in the middle. The gardener fills the bin with compostable material such as moistened newsprint, cardboard, dead plants, kitchen waste and red wiggler worms, the same components of a worm bed. The concept is that the worms will gradually decompose the material and their castings will nourish the soil and plants around the bin.

For mine, I decided to use an old garbage can with holes drilled in it. The garbage-can lid keeps out pests and any creature looking for a warm nest. I created the planting bed with building blocks set three high and cemented in place.  

Alas, I had a big problem with gophers, and I needed to win that battle. So this fall, when it was time to rework the soil, I put a layer of hardware cloth on the bottom. The hardware cloth helps to keep the gophers out. It won't last forever, but it will foil the varmints for a few years. Then a mixture of clean cardboard and soil was placed over the hardware cloth. Since the bed was already in a square keyhole shape, I added the garbage can and put soil around it to hold it in place.  

I fill this garbage can with the same things I put in my worm compost beds, including red wiggler worms. I have been watering it and feeding it for a few weeks to try to get it working. Eventually, the liquid and castings from the worms and other insects will work its way into the new bed areas and fertilize the soil from below rather than from on top.”  

Hunt County (TX) Master Gardener John Sanger explained more about the nuts and bolts of building an African Keyhole Garden for gardeners in hot, dry climates in the Hunt County Master Gardener Newsletter, “On the Grow”:

“The keyhole garden was developed in sub-Saharan Africa to help people gr