keyhole garden
ILLUSTRATION BY SARAH BECAN

The Most Brilliant Raised Bed We've Seen

Avoid wasted work, water, and space with the keyhole design.

May 22, 2015

If you’ve grown vegetables in raised beds you know they are amazing, often getting four times the yield of a traditional garden. But chances are, your design still isn’t as efficient as it could be. The solution? A keyhole garden. Keyhole gardens are round beds about 6 feet across, with waist-high walls. They get their name from their distinctive shape: a round column in the middle and a “slot” removed from one side, making them look from above like an old-fashioned keyhole. Said to have originated in Africa, where communities with very poor soil and a long dry season were looking for a way to grow fresh veggies as economically as possible, the shape is incredibly efficient, offers high yields, and can be built cheaply.

The round walls are stronger than traditional forms. And by eliminating corners, which often dry out faster, you maximize growing space. The central core (reach via the “slot”) holds kitchen scraps and filters gray water, removing the need for a separate compost bin. The combination of shape and central core also means that the wet compost keeps the soil moist, and the water radiates out to the plants, so your garden can stay lush during dry spells. Yet, since it is a raised bed, it also won’t get waterlogged in heavy rains.

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Most keyhole gardens are about 6 to 6 ½ feet in diameter, so a typical person can comfortably reach the center for planting and weeding. The outer walls are about two to three feet high, yielding a no-stoop gardening experience. Some keyhole gardeners keep a shorter outside wall but pile the soil up toward the central core in a cone shape, which adds area for growing.

Materials
The walls of the garden can be built out of almost any available material. Stacked stone looks nice, as do logs notched and stacked in an octagonal shape. You can also build a brick wall or use interlocking concrete blocks, available at most landscaping stores. Look for blocks that can be used to build a curved wall for best results.

Steps
1. Prepare the space by cropping existing vegetation as close as possible, but leave the top soil alone.

2. Mark the outline: pound a stake into the center of the garden and tie a short length of non-stretchy rope near the bottom. The rope should be your garden’s radius (half a circle’s diameter) in length. For instance, if you’re building a 6½ foot diameter garden, the rope should be 39 inches (3¼ feet) long. Then tie a sharp stick or nail to the rope, pull it taut, and mark the garden’s edges on the ground.

3. Draw a 1½ foot diameter circle around the stake to mark the central core. Leave the stake and rope in place as a guide for your walls. Then draw in the edges of the cut-out wedge, connecting the inner and outer circles. Think about how and where you want the wedge to be: if you plan to use the center basket to hold kitchen scraps, you may want it facing your back door, for instance.

4. Next, build your walls. Slide the rope up the stake as you build to serve as a guide for keeping your outside wall in line. 

 

5. For the central core, buy a small roll of sturdy steel wire mesh, such as chicken wire, as wide or wider than the walls are deep. Cut a length of the mesh and roll it into a tube about 1½ feet in diameter, securing the top and bottom so it doesn’t open back up. The size of the mesh isn’t critical, but an inch is typical. Stand the core in the center of the garden, with one side pressed up against the inner curve of the notch. Then make a pile of rocks, in and around the cage on the bottom of the garden. The pile should be about a foot high in the center, tapering down to a few inches deep at the outside edge. This will help excess water drain away.

6. Fill with soil, and you’re ready to plant!

Alternative
If you’re looking for a less permanent option or don’t want to build your own walls from scratch, you can buy a wall kit, such as the one made by Keyhole Farm. The metal conduit frame and rigid panels make it fast and easy to build a functional, bed and quickly begin planting.

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