24 Jun 2022

Keyhole gardens in the Growing The Future garden

Ardd Fotaneg · Botanic Garden

In this blog post, I aim to give you some information about where keyhole gardening comes from and why we’ve chosen to build ours out of the materials we have.

Where did the idea come from?

Keyhole gardening originates from Lesotho, in Southern Africa, and is so-called because the wedge shaped path and central composting space look like a keyhole. It was developed in order to provide a solution to poor soil and offer better growing conditions in an otherwise dry and harsh environment. By building up walls rather than trying to dig down, more moisture-retentive and nutrient-rich compost can be added on top of areas of dry, stony or depleted ground. Keyhole gardening allows for easy access to the whole growing space as the bed is compact and raised off the ground. The central compost bin means waste doesn’t need to be moved too far – weeds and pruning cuttings can be put straight in – and the nutrients from the compost will be worked back into the surrounding area by worms and other soil organisms.

Stones or blocks are usually favoured for building the outside wall as they will retain heat from the sun and have water retentive properties. There are also lots of options for buying ready-made or flat-pack kits, usually made out of plastic, they would be long-lasting and a quick way of setting up a keyhole bed. However, here in the Botanic Garden, we went with what we have around the site; showing that one of these beds can be made with materials you have to hand, keeping costs down and making use of otherwise unwanted materials.

Our Keyhole beds…

We have two keyhole beds – one made from pallets, with a more angular shape to it – and the other made from woven willow, which has a much more organic form.

The pallets are left over from our compost deliveries; these were easy to cut to shape and plentiful around the site. We stained them to give them a bit of protection from the weather so they won’t show up mud and dirt quite so easily. The only part of this construction that was bought was the eco membrane we used; there are many different membranes you could use to stop the soil from falling through the gaps in the pallets. The sections of the pallets were then screwed together and we used hazel stakes that were also harvested from around the site, to pin the sections of pallet in place. This bed is quite high but this extra height would be good when building an accessible garden – making it easier for people with less mobility or wheelchair users to reach the growing area and plants.

Our other keyhole bed is made from willow, also harvested from around the Botanic Garden site – lots of willow (Salix sp.) was planted as it is good for wet areas, of which we have many! Again, we used hazel stakes and wove the willow to make the structure for our bed. Make sure to get landowners’ permission when harvesting willow. It is a great material for building structures and is sustainable as the plant regrows each year – a wonderful addition to any garden.

All the materials we chose to use will not last more than two-three years and, after that time, they would need replacing – this is something to take into consideration when building your own. If you plan to use the structure for a long time, stones or bricks would be best.

Composting in your Keyhole bed…

As you can see from the photographs, we have used poles around our composting bins so that we can grow climbing vegetable plants. However, you could choose to put a lid or shelter over your compost area. This helps to stop the compost from drying out too much, keeps in the heat so composting can happen quicker and keeps some of the rainwater out so nutrients aren’t leached too quickly.

We hope these two examples can show you just how easy it would be to make your own keyhole bed. They are great for smaller spaces or, if you have the room, you could make several!

A special thanks to our volunteers Alison, Peter and Tom Stopp who took on the building of the keyhole beds, using their experience and passion for Permaculture techniques.