If you've never heard of a keyhole garden before, you might find the concept rather fascinating. Rather than planting in rows (or even in long, rectangular raised beds), which require a great deal of space for planting as well as harvesting, a keyhole garden—so named because of the notch-like gap in the center of it—allows you to make the most of a small area. To begin, all you need is a space that can house a circle that's 8 to 12 feet in diameter, with a small path to the center on one side of it... like a keyhole.
The average garden wastes a great deal of usable food-growing space in the paths between beds and planters. Every inch could yield a lot of edibles, but the inefficiency of standard gardening techniques allots that space to foot-traffic instead. Now, imagine what would happen if you took those rows or raised beds and curled them into horseshoe-shapes—you could wander into the middle of them so you could pick everything you needed, couldn’t you? Therein lies the genius of the keyhole bed: all you need is a little pathway that’s wide enough for you to walk into and turn around in comfortably.
Making the Keyhole Garden
To create your keyhole bed, measure out your circle of land, and determine how high you’d like the bed to be, and where you’d like to place the pathway. The most ideal placement is for the path to face southward, as that will create a U-shaped bowl that captures and holds heat. To map out your garden, mark the center spot with a stake hammered in place, and then measure out your desired circumference. Mark this circle with stakes, chalk dust, or even a shovel so you know exactly where you’ll be working. Be sure to delineate the central pathway, and use some sticks to keep that path clear.
Some people create wall barriers around their beds, while others prefer to leave theirs open. I’d recommend walling yours in, since placing a barrier around the bed will help to combat soil erosion and will also keep pets and other animals from getting at your plants, but it’s important to choose the right type of wall. Warm and temperate climates that don’t receive a lot of snowfall are ideal for wattle edgings and barriers, for example, which are easy to put together and create a gorgeous “country” look. Out here in Quebec, however, where it’s normal to have several feet of snow over the course of the winter, wattle just isn’t a viable option: we’ll be using rocks and stones for ours.
Once you’ve created your raised barrier, you can work on your soil. Using the lasagna garden method of soil-building, you can put down a layer of wet cardboard or newspaper as a base (black ink newspaper only!), followed by leaves and grass clippings, and then compost-rich soil.
Central Compost Basket
A technique that’s used in some keyhole gardens, particularly those in dry climates, is an active compost basket that’s placed in the center of the keyhole garden before the soil is built up around it. It can be created from chicken wire, woven reeds, or any other lattice that has fairly decent gaps in it. The bottom is filled with rocks to assist with drainage, and then straw and compost are placed in the basket, which is continually added to with organic, compostable materials throughout the growing season (grass clippings, vegetable peelings, leaves, and such.) This is watered regularly, and the nutrients from the compost will seep out into the rest of the bed, thus nourishing the growing plants.
In dryer climates, this also helps the garden retain moisture, as the wet compost keeps the surrounding soil moist. If your region is particularly dry and hot, you can place a lid over the composting basket to reduce evaporation even more.
Since I live in a fairly cool, damp climate, I haven’t used this technique and can’t vouch for it personally, but it has been used to great effect in many different countries, including several drought-stricken parts of Africa.
What Should You Plant?
Well, that depends on your climate and how much sun your garden gets over the course of the day, so once you’ve determined your zone and the amount of sunshine that’ll fall on your bed, you can determine which plants would be most suitable. It’s usually a smart idea to place the vegetables that will be picked the most around the central pathway (cut-and-come-again lettuces, culinary herbs, and such), with tomatoes, peppers, chard, and kale a bit further back. Along the farthest edge will be plants that are just harvested once, like root vegetables (carrots, beets, parsnips) and brassicas (cauliflower, broccoli, brussels sprouts). You can also tuck some companion plants and pollinator-attracting flowers and herbs throughout the bed, but be certain that the plants you choose are compatible with their neighbours.
If you’re a huge fan of tomatoes and will get enough heat and sun in your garden for them to thrive, you could create a garden that holds everything you need for all your favourite sauces and salsas, along with companion plants that’ll help your plants thrive. Choose a few different tomato varieties to grow along the middle of your garden bed, with herbs like chives, basil, and parsley around the keyhole path, and peppers, lettuce, and carrots towards the back. Intersperse some borage to attract pollinators and marigolds to fend off pests, and you’re set.
For our space, we’ll be creating what’s known as a “mandala garden”, consisting of multiple, connecting keyholes, as we have a fairly large plot of land that we’d like to use to its fullest potential, and some of the vegetables we plan on growing don’t play nicely side-by-side. One thing we plan to do, which might be of interest to you as well, is to plant sunflowers and pollinator-attracting flowers in the little nooks between the keyholes. We might also create some trellises behind the lower-growing plants for beans and peas to climb, especially in the beds that could benefit from the extra nitrogen the beans deposit, like brassicas.
If you’re looking for additional information about keyhole gardening, I’d recommend checking out the book Gaia’s Garden: A Guide to Home-Scale Permaculture, by Toby Hemenway, or the Edible Forest Gardens 2-book collection by Dave Jacke and Eric Toensmeier.
You can also pick up the recently published March 2014 issue of Texas Gardener Magazine: author Suzanne Labry worked closely with Dr. Deb Tolman to create a solid guide to keyhole gardens that are especially well-suited to a warm, dry climate.