Keyhole gardening is considered an “African survival strategy” in a land of scarce resources and unforgiving climate. According to reports from the BBC, 3 keyhole gardens can feed an African family of 10 for an entire year.
A humanitarian aid organization in southern Africa developed this particular sustainable gardening method. The design originates in permaculture which is a branch of ecological design & engineering that develops sustainable human settlements & self-maintained agricultural systems modeled from natural ecosystems.
A keyhole garden is the “ultimate raised-bed planter.” It consists of a circular shape w/ a 6 foot diameter & stands about waist-high. A notched-in section like a pie-shaped wedge allows access to the plants. It can be constructed from local recycled materials & incorporates a central composting basket into which food scraps/organic wastes are placed. The garden is also watered through this basket. It uses far less water than conventional gardens & recycles as it grows. From a birds-eye view this garden reminds one of a keyhole.
Keyhole gardening is an adaptable concept & almost any kind of raised bed of about a 6 foot diameter can be converted. The basic idea is functionality & efficiency: producing the most nutritious organic produce in the least amount of space using minimal water. Cattle water troughs, tractor & truck tires, old bathtubs, & boats are repurposed examples.
This concept has been replicated by landscape architect Dr. Deb Tolman in partnership w/ ranchers Jim & Mary Lou Starnater. Their property, located on the edge of the Hill Country in the community of Clifton, Texas is similar to southern Africa, “scorching heat, thin layers of topsoil, & elusive rainfall that can make for a brutal summer.”
We constructed our version in the Composting area using reclaimed materials & a bit of ingenuity. Kevin used heavy cord & a large screwdriver to scribe a 6 ft. diameter circle on the ground as our reference point. He and Roger set 4 ft. metal stakes to hold fence wire into the basic circular shape w/ an inset wedge to provide access (keyhole) to the garden. Into the center went the temporary vent/self-watering stack (later we’ll construct an inner basket measuring 1 ft. diameter & 4 ft. in height).
The students from Independence Life Preparatory School lined the interior and base of the keyhole garden structure w/ cardboard & set up alternating layers, 3 in. deep, bottom to top, of brown & green compostable matter. The inner stack will also be filled w/ alternating layers (kitchen scraps & other herbaceous matter) of green & brown.
Unlock your own Keyhole Garden
Follow these guidelines to get started:
1. Measure a 6-ft. diameter circle to define the inside wall of your garden.
2. Notch the circle (like cutting a wedge of pie) so you can access the basket at the center.
3. Construct the exterior walls about 3 ft. high using rocks, metal, timbers or any material that can support the weight of wet soil.
4. Use wire mesh to create a tube about 1 ft. in diameter & about 4 ft. high. Stand the tube in the center of the circle.
5. Line the outer walls with cardboard & fill the garden area (but not the wire mesh tube in the center), with layers of compostable materials, wetting down as you go. Fill the last few inches with compost. The soil should slope from a high point at the top of the center basket downward to the edges of the garden.
6. Fill the center basket with alternating layers of compostable material, along with layers of kitchen scraps & herbaceous weeds that provide the plants with moisture & nutrients.
7. Water the center basket & the garden only when the plants will not survive without it. This forces the plants’ roots down toward the center basket.
8. Feed the garden by adding more kitchen scraps, lawn clippings, etc. to the center basket.
9. Consider arching framework of thin wires over the garden. During the hottest months, the wires can support a shade cloth, & in winter, plastic sheeting creates an instant greenhouse.
10. Enjoy the fruits & vegetables of your labor!
Sources: Texas Co-op Power, Feb. 2012, pp14-15 “Keyhole Gardening: Unlocking the secrets of drought-hardy gardens” by G. Elaine Acker; http://www.urbanoasisproject.org/; www.sendacow.org.uk (Send a Cow Charity, Africa).