Keyhole Garden

Build a Self-Composting Keyhole Garden

For gardeners with a bit of unused space and a little ambition, keyhole gardens are ideal. They work like an organic recycling tank, using your food and garden waste as fuel to grow vegetables!

Keyhole gardens are a mix between square-foot gardening and herb spirals, blending the best of both practices to create something far more practical. In a word, the keyhole garden could be distilled down to ’accessibility’. It allows gardeners to access their garden bed from within a small radius located in the centre of the plot.

Square-foot gardening has as its premise the ability to carve up garden plots into…well…square feet. This can be done on an individual square-foot size thereby forcing the gardener to navigate the perimeter of each bed. The alternative method is to mark beds into square-foot dimensions of the whole which means gardeners need to bend down to cultivate, tend or harvest their plots.

So, while square-foot gardening has come a long way in reducing the amount of effort required to tend our garden beds it falls short of keyhole gardens by a long shot.

A keyhole garden offers as its main advantages the ability to tend your beds from one position. You literally work from within the bed and rotate to access every inch of it. Plus, the bed is raised so you don’t need to get on your knees when conducting your gardening tasks.

For people with physical disabilities, and the elderly, the keyhole garden is the ultimate way to enjoy this recreational hobby.

How do you build a keyhole garden?

To build a keyhole garden,  you will need:

  • garden soil
  • compost
  • well-rotted manure
  • wood ash
  • strong string
  • large stones, bricks or logs
  • straw or something similar
  • broken lengths of pipes, or old cans
  • worms!
  • several sticks or 1.5m garden canes

Find a space in your garden that’s about 3m2, with good sun, access to water, close to your classroom and relatively sheltered – clear it of weeds and dig it over.

Measure out the arm span of whoever will use the garden with some gardening twine. Halve this length and then add another 30cm – this is the ideal radius of your garden (you can make any size you like, however!).

Tie a stick to each end, plant one in the centre of your space and use the other end to draw your circle in the ground. Draw out an entrance triangle to your keyhole from the edge of the circle to its centre, starting at a width of 60cm.

Now take the sticks and create a basket by carefully hammering four sticks into a square with sides about 30-40cm long, make sure they are firmly in place.

Next lash the other sticks horizontally along the base, middle and top of the vertical sticks to create your basket – it should reach a height of about 1.3 metres, or at a level that can be reached by the children for watering.

Line the inside of the basket with straw (to keep the compost from falling out) and then fill with a layer of cans, then soil/manure, straw, ash, soil/manure and so on, until the basket is about two thirds full.

Keyhole garden construction. First, drive the stake, and lay the first course of stones.

Keyhole garden construction. First, drive the stake, and lay the first course of stones.

The basket has to be completed first, for the compost pile. It lets you recycle the old plant material right back into the soil, very efficient.

The basket has to be completed first, for the compost pile.

Keyhole Garden

Keyhole Garden done!

You’ll need to start by laying the largest stone, bricks or logs around the perimeter of the garden, remembering to create the entrance to the basket. The first layer is made up of the cans or old piping for good drainage. Now you can start filling the garden with the same layers as in the basket — the layers of mixed soil, then straw, ash, soil, ash and so on until the garden is at a height that your children can comfortably reach.

Also, if you can include some worms, they’ll help to circulate the soil. While you are filling these layers in, you will need to add more layers of stone, bricks or logs to your perimeter wall – effectively making a dry-stone-wall that holds in the layers.

If your wall is leaning very slightly towards the centre of the garden you are less likely to have a stone fall on your foot in the months to come! The wall can be made sturdier by packing soil into the gaps. Remember to make sure that the soil goes back into the garden in the order that it came out of the hole it came from: the top-soil goes on top!

You should end up with a mound, which slopes away from the basket – this increases the surface area that you can plant on.


Traditional keyhole garden in Africa

Your keyhole garden is now ready for planting!

You can segment the area into different crops to enable you to rotate them next season. Or, if you are a seasoned gardener, you will know how to do some intercropping and companion planting.

You can mulch with some wood chippings, old cardboard, leaf mould or something similar and put some colourful wool lines in to remind you what you’ve sown and to brighten it up a bit. To start with you’ll need to water in the basket and the soil surface until the roots grow.

Now you can carry on your composting by adding uncooked, organic food-waste into your compost heap or straight into the basket in warmer months, using the entrance.

Putting a circle of carpet over the top of the basket will help retain heat and speed up the composting process a bit. The water will now permeate the garden and water the roots of your crops with lots of great nutrients.

Why would I bother building one of these?

The ultimate answer, apart from the accessibility features mentioned earlier, is the efficient use of space. Consider creating a square, raised garden bed that you could access from every angle. It could only be 1m x 1m but would take up a space measuring 2m x 2m for access. Therefore, this one garden bed would require four square meters but only provide one square meter of gardening plot. The arable portion of this plot is only 25%.

A keyhole garden, on the other hand — with the measurements quoted earlier, would take up an area totaling nine square meters and provide a plot size of 5.8 square meters. The arable portion of this plot is a whopping 64%.

Even if you were to maximise the space used for the square garden beds the best percentage of arable land that you would get would still only be 36%, almost half that of the keyhole garden.

So, it makes complete sense to build these rather than waste valuable space constructing their square counterparts.

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