Updated: Oct 31, 2018
By Debbie Roland Master Gardener-Compost Specialist
If I knew then what I know now, I would plan a keyhole garden for the corners of my yard and maybe a few in the middle. It is a good way to grow almost anything in hot, dry places. If you take a bird’s eye view, a keyhole garden looks, well, like a keyhole. A notch is cut into a round garden bed which gives easy access to the compost area.
First introduced in dry African regions, keyhole gardening began as a way to help poor families develop the skills they needed to grow crops on infertile land.
I’m tall so I find that a 4-foot-tall bed works well for me but, as you can see from the pictures, the height isn’t all that important. However, the minimum diameter should be 6 feet. As you build your garden, it seems like it will take more soil than you will ever be able to find, but don’t worry, you will be filling it with other things as well and building your own nutrient-rich base.
In the middle of your garden, construct a round, porous, well-type structure. A piece of screen or hardware wire formed into a circle will work fine. This basket will not go all the way to the bottom of the garden but will only be about 18 inches below the soil level and have about 12 inches sticking out above. You will be dumping leaves, weeds (no seeds please), grass trimmings and kitchen scraps in here. This is also where you will be watering, which serves two purposes: it keeps your compost moist and when you water, and the water runs through your compost, taking nutrients to your plants.
There are a variety of recycled or natural materials you can use to construct the outside of your keyhole garden. I have two keyhole gardens. One is constructed of 1 x 6s that sit on the ground vertically like fencing. The other garden is in a tub that a friend found at a recycling center. It is about 7 feet in diameter and about 30 inches tall and originally was a syrup tub for livestock in a pasture. This one had a crack in the bottom which was perfect since it provided the drainage I needed in case of a heavy rain.
I have seen these gardens made of brick, rocks, cinderblock and even a discarded child’s swimming pool. Once your construction is complete, begin filling it with 4- to 6-inch layers from the ground up with wood, cardboard, compost, shredded newspaper, dry manure, worms, wood ash, straw and topsoil.
Next, repeat compost, straw and topsoil until you reach desired height.
When you plant your garden you will be surprised by how little water it actually takes. Check your moisture level frequently until you decide how often you will need to water. Gray water is used in Africa since water is in such short supply, and that may be something you want to consider as well.
Each year you will add materials to your bed as they decompose. I have added T-posts just inside the outside edge which allows me to add shade cloth in July and August. It also allows me to protect some late crops from frost. 3-17-2018