Keyhole gardens were first put in general use in sub-Saharan Africa to take advantage of their simple construction, water conservation and ease and efficiency of vegetable production.
The gardens are basically raised beds but with a unique structure and ease of access. There are many versions of the garden construction which may be found in the references below.
The gardens make use of different types of compostable materials in the main beds. This includes paper products, including lots of cardboard, manure, leaves, straw, old potting soil and often thin layers of soil are added. The top 5-6 inches can be compost, good garden soil or potting soil. This will be used for planting. The top of the bed should slope from the center tube downward to the outside wall to promote drainage.
The central tube, or well, is easily accessed from the “keyhole” cutout in the bed. There both green and brown compostable materials and kitchen wastes are added regularly. This is where the garden is watered as well.
The materials compost in the center well and water added leaches compost and nutrients into the surrounding bed. So the well both fertilizes and waters the root zone of the plants with little evaporation.
keyhole garden photos
Unlock Your Own Keyhole Garden
Follow these guidelines to get started:
1. Measure a 6-foot 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 wall about 3 feet 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 foot in diameter and about 4 feet high. Stand the tube in the center of the circle.
5. Line the outer walls with cardboard and fill the garden area (but not the wire mesh tube in the center), with layers of compostable materials, wetting it down as you go. Fill the last few inches with compost or potting soil. 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 and herbaceous weeds that provide the plants with moisture and nutrients.
7. Water the center basket and 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 a framework of thin wires over the garden. During the hottest months, the wires can support a shade cloth, and in winter, plastic sheeting creates an instant greenhouse.
10. Enjoy the fruits (and vegetables!) of your labor.