Keyhole gardens are commonly seen in permaculture because they are beautiful and productive, ideal for small spaces, and can accommodate a variety of plants, annual vegetables, herbs, and flowers. The garden is constructed from low-cost, recycled, reusable, and locally-available materials, and uses a number of layers to nourish the soil, making it more productive. An added benefit is that these are efficient, more productive, yet using fewer resources and less water than a conventional garden. This makes Keyhole Gardens perfect for attaining sustainable, small-scale agriculture.
When finished, the bed will stand at about knee- or waist-height, allowing you to reach all parts of the bed for harvesting, while still giving you enough room to grow a number of different plants. Making your raised beds be at the same height of your knees, or even a little higher, are most preferred, as it reduces the need for bending or stooping, while also giving you the optimum space needed for harvesting versus planting space. Keyhole Gardens and Raised beds, in general, are well suited for nearly any plant, especially perennials, which have deeper root systems and require less water.
First used in sub-Saharan Africa to reduce food insecurity and empower local communities, keyhole gardens are catching on in the developed world because of their ease, low-cost, and usefulness in locations with dry climates and poor soil conditions. Although it is mostly a modern technique, similar practices go back in time for centuries, beginning around 300 B.C. with the Quechuas of South America, and it’s still being used in Bolivia and Peru today.
Keyhole beds offer easy access to crops when gathering, as well as making it easier and more efficient to tend the garden. The soils in the beds require no digging or tilling, preventing disruption of soil ecology, and reducing erosion while also mulching to increase moisture retention. Because the soil is continually kept loose, moist, and supplied with nutrients, the beds are very energy efficient, and improve soil quality over time. This allows the micro-fauna living in the ground around the plants’ roots to multiply and go about their work of building healthy soil, whilst giving the gardener easy access for planting and maintenance.
Technique and Designs
Standard gardening techniques, with single rows of plants interrupted by small passageways, or footpaths, allot about half of the usable space for walking, which is inefficient and wasteful. Raised beds can help reduce that wasted space. For example, placing walkways between every three or four rows can cut down the wasted space to about 30 percent. Although, it makes those middle rows more difficult to reach, because they are packed tightly in between a smaller space, which you cannot walk to, but must scoot through slowly and carefully, going side-ways in one way and out the other.
Another way to cut down on this wasted space, and improve on the design, is to curl the beds into horseshoe-shapes, wrapping a straight, raised bed around an entrance and walkway to create a circular shape. Rather than planting in straight rows or long, rectangular raised beds, planting in a circle is much more efficient, fitting more plants into a space
The circular shape and keyhole feature allows you to maximize the available planting space by cutting down on the areas taken up by walkways, so that less than a quarter of the ground is surrendered to paths. This thereby utilizes a greater space for planting and increasing yields.
One such bed is the Keyhole Garden. These are usually about 2 meters in diameter and 1 meter high. Keyhole Beds are so-named because of the notch-like gap in the center, which holds a composting basket containing organic kitchen waste that moistens and nourishes the soil. Connected to this notch is an open pathway that runs through the middle of one half of the bed and creates a walking path to the to the outside, allowing easy access to the plants. The combination of the center basket and the entrance-way gives the garden a keyhole shape when viewed from above.
This shape provides easy access to the crops and compost-bin with a minimum path-to-bed ratio. Because of their simple design, Keyhole Garden beds can be constructed into almost any shape, including straight rows, wavy patterns, or more complex, geometrical designs. They can be adapted to make different and creative patterns, rather than conventional rows, to add more edges, and increase the efficiency, diversity, and productivity of the garden. Winding paths will increase edges even more. In addition, they can be built either as stand-alone beds, or combined into a series of nested structures with extra access points branching from a central path.
It can also be modified by combining it with a wicking bed design to make for a highly efficient and productive, self-feeding, self-watering growing system. Although, Keyhole Gardens are meant to provide drainage through the garden. And wicking beds alter the mode of this drainage, so combining Keyhole Gardens with a wicking bed would change its design, use, and application considerably.
The added benefit of the raised garden is that it acts as a thermal-mass. The mound absorbs and stores passive solar energy. They can be integrated with an internal compost bin that generates its own heat, so heat-loving plants can be grown with less direct sunlight. This helps to extend the growing season, prevents soil erosion, and produces a more regular crop. For small gardeners, keyhole gardens can keep producing throughout multiple seasons and conditions, and as few as three beds can supply a large family with vegetables year round. They are also very versatile, protecting plants against the harsh climatic conditions of hot, dry, and cold environments, making them perfect for anyone who wants to grow productive, organic plants in any climate, in a small space, with little effort.
How to Make a Keyhole Garden
The number of designs for your raised Keyhole garden are potentially limitless, but the ones that will be covered here include the original, African-style circular beds; Mandala Gardens; and sectional or parallel rows. The size, design style, and composition of your bed will depend on a number of factors, like the available space for cultivation, your mobility and reach, the materials you have available, and the number of plant species you wish to grow. Any building material is feasible, as long as it is strong enough to hold the growing medium and does not biodegrade.
One of the many benefits of this garden bed is that it can be built from recycled materials, making use of wasted resources and locally sourced supplies. Bricks, cinder blocks, rocks, timber logs, wooden pallets, or metal siding could all be used to build the retaining wall to hold the growing medium. Other possibilities include: bamboo sidings, old row boats; water troughs; tractor and truck tires; bathtubs; earth bags; milk jugs; beer, wine, or soda bottles stacked together and mortared with mud or cement; cans or plastic bottles filled with sand and bound with clay.
The number of potential substances you could use to make the walls is potentially limitless, and just about anything could be used, as long as it can hold the weight of the soil and plants. However, different materials will create different microclimates within and around the bed, which you may take advantage of by choosing the right physical components. For instance, rocks retain heat more than timber, and bottles could be placed under the beds for added drainage, which can provide a wider variety of growing opportunities. Larger keyhole gardens can also be constructed with a featured plant or focal point in the center, such as a small ornamental tree, shrub, or water feature.
In especially deep parts of the planting bed, if you have big planters, you can put a big stone on top of the dirt next to your plants to give you a place to put your hand when reaching into the planting space. This way, you’re not constantly smashing down plants and compacting the soil any further. If not using bricks or stones for the walkway, you can add some poles or weavers on the sides to hold the dirt and give it greater support, keeping the beds from collapsing onto the pathway. Simply place them along the path, every few inches or so, and ram them into the top soil with a mallet.
If you’re growing in shady conditions, or if you want to plant more sun- and heat-loving crops, you can build your beds on a slope that tilts slightly to the south, towards the sun. This should help your bed to absorb more warmth during the day, and extend your growing season even more. In this case, the walls of the bed will have to be built unevenly, so that one side is higher or lower than the other, in order to achieve the desired angle. You can also orient the walking path to face south and use it to create a U-shaped notch that acts as a sun trap. Or, alternatively, you can orient the path to face north to reduce evaporation and create more shade.
Building a Circular Bed
Step 1: Location
To begin, choose a flat, circular space about 3 m in diameter, situated near your house or along a main pathway for quick access.
Step 2: Measure and Mark
Insert a stake into the middle of your location and tie a measured piece of string to it, and cut it down to about 1.2 m long. To get the right sizing, use the length of your arm as the radius and add a few inches on top. Your aim is to be able to reach any point of the raised bed from the inside of the keyhole. Then, mark out the circumference of a circle where you want to site your bed with the stakes. This will define the outer perimeter of your bed, and should be about 6-7 feet in diameter.
Next, mark another circle in the center with a diameter of 45-50 cm, or about 2 feet, across. This is where you will site the central composting pile. If you want, you can build up the center a little bit to make the bed slope away from the center. This allows better transfer of water and nutrients to the outer plants, and also adds to the surface area.
When finished, choose the location for your keyhole at some part between the inner and outer circles, pointing to the outside. This is where you will stand and move when gathering crops. Once you have chosen the right spot, mark off a 2-3 foot section along the edge. Then draw a straight line from both ends of this section to the center, connecting the two circles. This will serve as your keyhole access path and walkway. The final shape should make a wedge or notch through one side, resembling a pie with a slice cut out of it.
Step 3: Clear the Ground
If your soil has any roots or rocks, dig down by about a foot and remove them. If not, then simply dig up the first few inches of top-soil, and turn it over to loosen it up. You can optionally dig around the central circle and the keyhole walkway, cutting a clear line with a spade to define the edge where the wall will be built. Then, dig a small channel around the edge of your area to allow you to slightly bury the first row of bricks in the ground, increasing the structural support for the wall.
Step 4: Building The Outer Wall
Building a solid wall around your garden creates a barrier that prevents soil erosion, and keeps pests and other animals away from your plants. Construct the outer wall of your keyhole bed alongside the edge by building around the perimeter of the lines you drew.
Start by laying down your bricks, stones, or other building material in your desired configuration, arranging them in a circle around the perimeter. One strategy is to use bricks, tilted roughly at a 40 degree angle, laying them on top of each other in a circle, but remember to leave the access path open. You can build the wall with stones, boards, wood, or anything that will hold dirt in your desired shape, up to a height of about 3-4 feet.
If using rocks, choose big ones flat enough to be stacked. To increase the structural integrity, dig a shallow trench along the circumference of the circle and place your flattest stones around its perimeter. This should provide a stable base for the rest of the wall, which can be built out of larger, bulkier stones. Bricks are also a bit easier to set into the ground for the tighter quarters of the keyhole walkway, and can be buried partly in the ground to secure them. Additionally, you can pave the keyhole area with rocks or bricks so you can stand or kneel down without getting covered in mud. You can also add a second layer of bricks to the rear to make the back sturdier.
After finishing the walls, check to make sure it’s still in an even circle, and remove any bricks or rocks in the way of the entrance. Then, dig holes on the sides of the opening to place posts to define the corners of the barrier. Within these holes, insert two posts about 1 foot deep on either side of the keyhole entrance. Be sure to make the entrance about 50 cm wide. After that, start laying the 2nd row of bricks. At this point, it won’t have very much strength, but when more layers of bricks are added, the strength will increase. But when you stack the bricks up to about 3 or 4 layers high, then the wall should be quite strong and sturdy. Build the entrance by laying the bricks flat along its edge, going in by about 50 cm. To cut the bricks to the right size, use a big chisel and a hammer.
Step 5: Making The Compost Bin
To create the basket area for the compost bin, you have to make a lattice to hold it in, using either wooden sticks, a chicken-wire or metal mesh, poles, canes, woven reeds, or another material. Take some wooden sticks, about a meter long, and insert them into the ground vertically along the perimeter of the inner-circle. Once you have plenty of canes lined around the perimeter of the inner-circle, tie them securely with some string to hold them together, but leave some slack to allow you to loosen or adjust it later, if needed.
Next, get a piece of wire mesh, chicken wire, or any other lattice with gaps around 4 feet tall. Roll it into a tube about 1 foot in diameter, and place it in the center of your bed, inside of the sticks and string. This will serve as the compost bin, into which you can place kitchen scraps and other organic materials, providing the keyhole bed with a constant supply of nutrients. It will also soak up moisture, facilitating automatic watering. You can also opt to go without the chicken wire, if you want, although you may have to use more sticks and string to hold in all the food scraps, or use another method to hold up the dirt.
The compost bin itself can rise up and above the garden, with the mound sloping down from the center. In this way, as the food scraps in the middle of the bed degrade, they will flow down and outward spreading their nutrients to the plants around them. When you water the compost, water and nutrients seep out into the surrounding soil. The center opening is used to irrigate the whole garden, bringing nutrients from the compost into the surrounding soil. It also adds more and more soil year after year, building up the level of the ground in the bed. To ensure adequate irrigation, and a persistent supply of nutrients, and be sure that the compost bin is spaced no more than 3 feet away from the plants.
Step 6: Filling The Bed
Sheet mulching is another useful method to keep out roots and weeds. It also adds carbon, nitrogen and air to the soil, making it very useful for Keyhole Gardening. After building the wall up by one or two layers, then put down a layer of untreated cardboard or black-ink newspaper, covering the growing area of your bed. But don’t cover the walking path or the center circle, if you can manage it. The paths and keyholes only need a layer of straw over the base sheet mulching. To improve drainage, first put down a layer of pebbles under the sheet mulch, or use a large grouping of vertically-standing plastic or glass bottles, bound together in large bundles to create a layered section of vertical columns, to create open passageways for the water to pass through. Optionally, you can make a walking area around the bed, and in the central pathway, by laying a weed sheet on the ground and covering it with stones. Also, consider using a weed-liner in the bed, lining it up the inside of the walls, to keep the soil from falling out of any cracks in the walls.
Next, fill in the growing area with soil, compost, and straw layers. On top of the sheet mulch on the bottom of the bed, start by laying down some larger high-carbon items, like timber, sticks, and twigs. Next, add a layer of straw, and then layers of soil and compostable materials, like manure, worms, wood ash, straw, and coffee shells. Ideally you want a ratio of about three to one of brown to green materials. If you can’t get ahold of the ash, limestone can be easily substituted because both materials maintain the neutral balance of the soil and compost pH. Follow this with leaves and grass clippings, and then finish it with compost-rich soil.
Continue filling the area inside the bed with more compost, straw, and topsoil, going around the center bin, and watering each layer as you go, until you reach the desired height. You may have to build up the wall as you fill in the bed with soil to hold the dirt inside. At the top of the pile, add a few inches of potting soil and some compost to create a rich potting-base on the surface to stimulate the plants. As the material in the bed decomposes, the heat generated will serve to break it down and turn it into rich soil. And, over time, the garden will grow in height as the compost adds more volume. This way, you will have to build up the wall on the sides to accommodate the increasing size of the bed.
Step 7: Filling The Compost Bin
This central composting bin serves four purposes: it retains moisture and provides nutrients for the plants; it builds up new soil over time; it promotes strong root growth for the plants, as their roots are attracted to the nutrient rich area and penetrate more deeply into the soil; and it should also, in combination with natural rainfall events, supply sufficient water to feed the plants.
After filling the bed with soil, tie more string around the protruding canes at the top of the mound to allow the middle to be filled with garden waste, stacking up high above the bed. The central compost bin should rise up above the soil level in the bed when it is finished. Inside the compost bin, fill the bottom with a mound of small- to medium-sized rocks to assist with drainage, and then add green composting material until full. Place a garden sieve on top of the compost bin to allow the rain water to seep in and help enrich the soil. This way, when it rains, or when you water your compost, the nutrients will seep out of the compost, and slowly be distributed into the surrounding bed.
During rainy spells you might wish to cover the compost so the nutrients do not leach out too rapidly. In addition, keeping a tight lid on the center will retain heat and reduce evaporation. Optionally, you can construct a small roof over the bed or the compost bin to deflect rain and regulate compost moisture. If the plants need manual watering, simply water directly onto the compost bin in the center with rain water or grey water from your kitchen. Be sure to re-fill the bin regularly with food scraps and garden waste to ensure that the soil remains high in nutrients.
Step 8: Plant Your Keyhole Bed
When you’re ready to plant, add a bit of soil or sand to hold your seeds, and cover it with straw or old hay to keep it moist. Now you can plant your seeds or transplant your seedlings. The species that you plant will depend upon your personal taste, climate conditions, water availability, and how much sun your garden gets throughout the day. If your bed gets 4-6 hours of sunlight per day, depending on the time of year, this may limit your growing options to mostly leafy vegetables. But if your garden gets more sun (up to 8 hours per day, or more), then you can grow almost anything. In the summertime, try growing Malabar spinach, which loves the heat. Chard can grow all year long. If you live in a rural or semi-forested area, use some stakes and plastic netting to keep deer away from your garden.
It can be useful to approach your keyhole bed as a zone-system in miniature, with each bed being comprised of three concentric circles or rows, inside each of which is planted different varieties of plants to create micro-climates within the zones. Place the fastest growing vegetables (lettuces, salad greens, herbs), in the first circle around the pathway, closest to the center. The next circle out should be comprised of slower growing plants (like tomatoes, peppers, peas, chard, and kale), placed a bit further back from the inner-section. The furthest zone, in the back, should have the plants that will be harvested least often, like root vegetables (carrots, beets, parsnips, onions) and brassicas (cauliflower, broccoli, Brussels sprouts), placed along the farthest edge.
You can also plant the beds using guilds. This can be used to generate different micro-climates in the garden, or combine species that benefit one another through their proximity by providing shade, fixing nitrogen, repelling pests, etc. For instance, placing taller plants on the edge of the bed can help protect lower-lying plants from damage by the sun or wind. You can also build some trellises behind the lower-growing plants for nitrogen-fixers and climbing plants like beans and peas. When planting, include tall elements around the back edge of the garden to provide shade, with increasingly shorter plants moving towards the opening in the center to create a sun trap. You can also plant pest-repelling flowers and herbs, like basil, chili, garlic, rosemary, and rue along the perimeter and throughout the bed. Also, consider taking advantage of companion plants like nasturtiums, marigolds and calendula.
One example of a small guild-system to use is the “tomato-polyculture keyhole”. The bed can be around six feet across and three rows deep: one near the path, one in the middle, and one in the back. Plant herbs like chives, basil, and parsley in the first row, around the central path. Then, plant a row of a few different tomato varieties in the middle of your garden bed, followed by peppers, lettuce, and carrots in the last row, towards the back. Additionally, try using a planting of Jerusalem artichokes or sunflowers to act as a wind-shelter and reflect the sun. Intersperse these with some borage to attract pollinators, as well as marigolds to fend off pests.
Kiwi (on trellis)
Most traditional gardens follow a linear planting path, which has its origin in the private ownership and control of land, the need to mark and measure, and the use of mechanical soil cultivation. However, none of these elements necessarily apply to permaculture, which permits a free-form approach to agriculture, allowing for a non-linear garden design. These sorts of gardens are beneficial because they are more productive, due to the fact that a non-linear geometry allows more surface area to be used, and they also permit a greater diversity and integration of elements. Furthermore, it can be modified to respect the form of the land, to work with the flow of water, and to accommodate the way humans live and move to make for a more efficient, more beautiful, and more productive garden.
If you have a large space to use, and plenty of time and resources to devote to a bigger project, then you can construct what’s called a Mandala Garden. A Mandala Garden is based on the keyhole garden, but instead of a single garden and keyhole, it consists of a large garden, or many gardens, with multiple connected keyholes, using the combination of many horseshoe shapes to create a larger structure, shaped like a mandala. The keyholes can be used along a pathway, or they can be combined around a circle, or another shape, to create a beautiful mandala garden.
The primary reason to build a Mandala garden is twofold. The first reason is because it is aesthetically pleasing; and the second is that it is a time, space, and resource saving design. The reason for this is that, by having the bulk of your vegetable beds in one large circle, you only need to have a single sprinkler in the center, which you can use to water the whole garden via a single tap, vastly simplifying irrigation.
Although the mandala garden will supply enough space for a wide variety of plants, you will probably still need extra beds for mass plantings of vegetables such as potatoes, onions, pumpkins, etc. You can also make the center of your mandala a useful feature in some way, like a small pond, or turn it into a special area, planted with herbs, flowers, a small tree, or a shrub.
Building The Mandala Garden
Choose your site in a sunny spot on a flat piece of ground and decide on the diameter of your mandala. If you are gardening on a gentle slope, the shape of the beds will follow the contours, resulting in a beautiful and functional geometry. The diameter of the garden should be about equal to the circle made by your sprinkler when on full pressure. A size of six to eight keyhole segments is convenient. Mark it out from the center point using some pegs and string, and draw out where you will place the keyholes.
When drawing out your keyholes, form it out of a keyhole-series, radiating from the center of the mandala, with an entrance or keyhole going into the middle of each segment. Or, form a keyhole from the center of the outer-curved edge of each segment, going in towards the center. Be sure that every part of the growing area is within arm’s reach of the walking path, allowing for easy pickings of the crops.
Use your bricks, stones, or wooden pegs to form the segments of the walls, leaving enough space between for a narrow walking path.
Lay down some sheet mulch over the growing areas inside the circle, using thick wads of overlapping wet newspaper, cardboard, or organic carpet, and water it well.
Fill in the beds with top soil, straw, kitchen scraps, lime (if required), aged manure, and compost. Then, top it off with more of the mulch of your choice, like straw, alfalfa or lucerne, rice husks, or a sawdust and manure mix. At a minimum, cover the paths and keyholes with a layer of straw over the base sheet mulching, which can be topped up occasionally. This will cover the ground enough so that you can walk over it easily. Keep your beds mulched with wheat straw and your paths mulched with pine straw, as the pine straw allows you to move around in the garden right after a rain. You can also leave the paths bare if you want, and add stones or bricks over the open ground to create a solid walking-surface.
Sit back and wait until spring before planting to allow the worms to do their work. You can also plant some chop-and-drop crops for mulch later to be slashed and left to rot before your spring plantings. Or, use nitrogen fixers, which will naturally nourish the soil. When ready to plant, mark out your mandala circle and plant a crop of potatoes in mulch using the no-dig method. After harvesting the potatoes you will find the soil softened, enriched and worm-infested, making great growing conditions for other plants. After each cropping season, feed the mandala with manure/compost, lime, and blood and bone to keep the worms happy and replace lost nutrients.
Sectional, Parallel Beds
Different variations of raised, parallel planters exist. The simplest option is to make multiple long and straight raised planters with timber sides, about knee-high, with paths going along the sides. Sometimes they have tall rear layers, like trees and shrubs, but usually have lower plantings and look a lot like normal raised beds. Straight planters are useful for rotation cropping, which prevents excessive build up of certain pests in the soil (e.g. nematodes, phytophthora etc.), as you only need to rotate your planting regime by one segment each season. They are also easy to water using drip irrigation and a thick layer of mulch, which will reduce the amount of water required by about 30 percent.
One design option is to take a veggie patch of about 25 ft. x 50 ft., and split it in half with a new path going down the middle, creating two identical square garden areas on either side with a walkway between them. Then, turn the two opposing ends of the garden into new beds, parallel with the new path. Alternatively, you can take two of these beds, running parallel to each other and separated by a path, and merge part of them together into one bed with a keyhole inlet. This allows you to use some of the old walking path as a growing space.
The second option is to take these straight, raised beds, and put in some keyholes to give it crenellations. Put the keyholes in through the sides of the bed, spaced equidistantly every few feet or so,
The keyholes can be deep or shallow, depending on your needs, but at the least they should go in by 1-2 feet, or just enough to provide easy access. When planning for a large bed, you can alternate the keyholes on the sides so that one sinuous, wave-like bed is created, without branches. This allows the bed to be watered with a single soaker hose via drip irrigation. That greatly simplifies your needed supplies and infrastructure for watering, and allows you to use cheap, recycled rubber-soaker hoses, which should work fine with very low water pressure.
The third option is to not use keyholes, but to plant in wavy rows as opposed to straight rows. The benefit of using wavy rows is that they provide more plants in the same area as straight rows. They can also be built with paths on contour to create bioswales without extra digging. With this, you wouldn’t need separate beds. Instead, you could change crops every 10 feet along the swale.
Another design option is to base your garden design on the veins of a leaf. This way, the main branch consists of a path in the middle that leads to the center of the garden, wide enough to get a wheelbarrow through. This main path then branches off into smaller paths, wide enough for a person to work and move, but too small for the wheelbarrow. These, in turn, branch off into smaller paths.
Frames and Drainage
When building with wood for the walls, you can install a 2×4 shelf along the edges of the frame to provide a comfortable seat. It will also to keep the sides from bowing out under the weight of the soil.
Constructing a roof or barrier above or around your garden is useful to protect it from pests and the environment. You can incorporate a frame into most of your designs to support a shade cloth or an umbrella during the hottest months. This will shade the plants and reduce the heat and sun exposure by about 60 percent. The frame might also be covered over the top and the sides in early spring with plastic sheeting to create a greenhouse. Several focus group and interviews with builders in the developing world revealed that saran wrap is the ideal material for this, while other members suggested clear greenhouse plastic. Other feasible alternatives to use to form the roof include: recycled materials (glass bottles, tires, etc.), lamina roofing material, cinderblocks, or bamboo and wooden sticks. While building the roof, it’s important to take into consideration what local materials are available to use for construction. The materials used, and the design of the roof, may depend upon what is most readily available to the individuals constructing the garden.
Some disadvantages of certain keyhole garden features pertains to drainage, as their capacity to withstand environmental factors (like heavy wind and rain) may be limited, requiring the maintenance of sufficient drainage within the keyhole gardens.
In order to facilitate drainage, two varying drainage systems have been implemented into some experimental keyhole gardens using recycled resources and other local materials. Several drainage item options include halved tires, inverted plastic crates, inverted plastic or glass bottles, and bamboo shoots. These materials, especially used tires and plastic bottles, may require further research and experimentation to ensure that they are safe for food production.