By: Ash Lloyd, EcoHouse Green Gardening Volunteer
About Keyhole Gardens
Keyhole garden beds are raised so that someone working on the garden can lean against the walls for support and the total radius of the garden is kept small so that the entire bed can be reached easily. This makes it a great garden option for the elderly, chronically ill, or those with disabilities who would typically find ground level garden beds difficult to tend to comfortably. Over the past couple of decades, it has made its way to North America, where it has become increasingly popular among gardeners who practice permaculture. Permaculture is a gardening design and management philosophy that focuses on creating gardens that take full advantage of natural nutrient cycles in order to create sustainable gardens that can grow for generations without the need of artificial fertilizers.
The structure of the keyhole garden is that of a raised, circular garden bed with a hole in the centre and a “notch” cut out of it to provide access to the garden’s centre, which is where it gets its name from. The hole in the garden’s centre serves as a receptacle for compostable waste like non-animal kitchen scraps, and is typically made out of chicken wire or some other permeable material that will allow the hole to maintain its shape.. The scraps are placed into the central receptacle and watered to help them break down properly, as well as to deliver water to the garden’s subsoil layer.
A keyhole garden’s outer walls are typically made from stone or brick, but rot resistant wood or even plastic have been used as well. The garden’s radius is typically only 1 meter (3.2 ft) from the centre and its height is typically 30 – 60 cm tall; some designs use a tiered structure with a taller section around the middle to allow for a taller central cavity to create a greater compost capacity. Some people also put composting worms, like red wigglers, into their compost silo in order to accelerate the breakdown of organic matter through vermicomposting. This is only recommended for warmer climates, as red wigglers are not able to survive the temperatures of a Canadian winter.
The keyhole garden can be used to grow almost anything, however there are definitely some types of plants that will take to it better than others. Plants with wide and intensive root systems will not do as well in keyhole gardens as plants with deep tap roots or small surface level root systems due to the small nature of the garden. As such, plants in the nightshade family (eggplant, tomato, potato) will not do as well as root vegetables like beets and radishes, or leafy greens like lettuce and kale.
The keyhole garden is low maintenance when constructed properly and can make an excellent kitchen garden for plants you use often and want fresh, like lettuce or herbs.
Example – My Own Garden
For this article I actually have an example of my own to share with you. This spring, I built my own keyhole garden on some unused scrub land nearby. It was made almost entirely from materials I found laying around and the only things I really needed to bring myself were wire for the composting silo and some compost. I started in the spring around May, a few weeks before the last frost, and began marking out the space I wanted to use. Once I knew where I wanted to put it, I went about collecting loose rocks and piling them up around a stout, wicker-like fence to allow the wall to retain its shape without soil in the centre. I filled in the gaps between the rocks with some local clay-rich soil in order to help the bed retain moisture. When the outer wall got to a height I was satisfied with, I lay down a layer of gravel, logs, and then sticks in the interior before finally laying down a fairly thick layer of soil with some compost mixed in.
I planted my seeds and transplants a week or so after last frost, and most of the things I planted grew prolifically over the course of the summer before gradually dying back in the fall. I had plenty of kale, mint, peas, and cherry tomatoes for the whole growing season and I’m looking forward to seeing how the garden does during its second spring.