Keyhole gardening is a method through which recycled materials are used to sustain a garden in otherwise unfavorable conditions. Keyhole gardens are most common in developing countries where arable land is scarce, or arid climates that do not usually sustain typical garden lots. They are a form of raised bed gardening that will nourish plant growth and utilize composting, recycling, and minimal water. They also provide protection from many animals and make tending easy and almost effortless.
A keyhole garden is built in a circular pattern, usually no more than 12 feet in diameter, on a base of small rocks, pottery shards, sticks, broken containers, or other materials that will allow drainage. A chicken wire or mesh wire cylinder is placed in the center of the circle high enough to jut a foot or so above the top of the soil level.
Notch the circle (like cutting a wedge of pie) so you can access the chicken wire basket at the center. Construct the exterior wall about 3 feet high using rocks, metal, timbers, stones, bricks or any material that can support the weight of wet soil. Vertical limbs, metal rods or planks driven into the ground can help provide strength and support walls. Serious gardeners can use mortar to hold walls in place.
Line the outer walls with cardboard or other biodegradable material, boards, limbs, etc. 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. Composting bacteria can be sparsely added, too, especially in the center tube, to help aid in the breakdown of organic material.
Fill the center basket with alternating layers of compostable material, along with layers of kitchen scraps (no meat or bone scraps that draw animals or insects, and smell bad) and herbaceous weeds that provide the plants with moisture and nutrients. Vegetable peels and rinds, coffee grounds, egg shells and other organic food waste make the best fill.
Water the center basket and the garden to start, and then only when the plants will not survive without it. This forces the plants’ roots down toward the center basket. Feed the garden by adding more kitchen scraps, lawn clippings, etc., to the center basket. Any regular garden plants or herbs can be grown that will utilize the sun and climate where you are. Shorter ones may be better choices to fit space and height needs, and so one can reach to harvest the crops since the bed is already raised 2-3 feet. Bush beans, peppers, compact tomatoes, and other non-sprawling plants, and many herbs work well.
Consider arching a framework of thin wires or mesh over the garden. During the hottest months, the wires can support a shade cloth, and in winter, plastic sheeting creates an instant greenhouse and lengthens the growing season on both ends. The structure also prevents or discourages animals and birds from eating the plants and crops.
Keyhole gardens are used extensively in Africa, where rainfall and thick layers of good soil are scarce. In the American Southwest, they can provide fresh produce in areas where drought conditions have continued for many years. In flash floods, they stand a better survival chance than a flat bed, especially if judicially located.
Keyhole gardens can provide sustainable food sources for people seeking to step farther off the grid, conserve gardening resources, and provide an additional holistic avenue for recycling materials.