The base of the compost bin is typically lined with rocks to aid in drainage. In this layer, you can use broken tiles, pots, twigs, and even branches. This first layer of twigs, sticks, and hardy debris continues into the base of the planting area. Ideally, as you prepare the planting area, the soil is sloped away from the compost core, enabling water and nutrients to flow out and reach the outer edges.

With the compost bin set, the outer walls built, and the initial layer laid, you can now begin to layer the soil of your planting area. You will want to build in layers of soil, manure, ash, and other organic matter. If you need to add extra structure to your keyhole bed, you can add additional layers of twigs and sticks around the planting area. This method of layering is often referred to as “lasagna mulching” because of the many layers of compostable materials. 

The planting bed layers will gradually decompose over time. As they begin to shrink, you can top them up with another layer of lasagna mulching. So as not to interfere with the crops, wait until you are finished harvesting for the year to add more mulch.

How does the keyhole bed work?

The keyhole bed has many benefits from its design. First, the compost bin provides essential nutrients to the bed. As you build your compost heap, the plant material breaks down, releasing the nutrients to the surrounding soil. Dr. Deb Tolman, who has years of experience building keyhole beds in Texas, recommends using a compost core ratio of 3:1 carbon-rich brown compostable materials to nutrient-rich green material. Examples of “brown” compostable materials include leaves and wood chips. Nutrient-rich “green” material includes kitchen scraps like peelings from fruits and vegetables and grass clippings.

These resources can be gathered from your home and garden to fill the bin, which also reduces your home’s trash going to the landfill. You can then add water the center basket, creating a compost tea as it filters through, taking water-soluble nutrients to the roots. This method of small-scale farming demonstrates that even on the most malnourished property, a properly made garden can become an oasis of life. Just be sure to keep filling the compost bin at the center of the bed!

Since the keyhole bed was designed for arid regions, it is inherently more drought tolerant. The wooden debris lining the bottom helps absorb moisture. By placing a thick layer of mulch on top of the soil, you can further add to your water retention. In particularly hot climates, construct a shade to protect the top of the compost basket. By blocking the direct sunlight and intense heat, you prevent the drying of your compost.

Why build a keyhole bed?

Since keyhole beds can be made of many different materials, whether purchased or salvaged, it makes them an affordable option for any home. And though most designs are a horseshoe shape with an edge for easy access to the compost bin, you can modify them to fit your specific needs.

They can be built as a permanent feature on your property, specially designed to be an aesthetically pleasing addition beside the kitchen. Keyhole beds can also be temporary, easy to disassemble and move if you are keen to fill a spot with food until you’re ready to build that add-on.

Also, having your plants raised above the ground alleviates back strain of harvesting. You cut down on how far you have to bend to reach the plants, making maintenance easier. And by planting strategically, placing climbing vines against the compost bin, trailing vines on the edges, and an assortment of beneficial plants in between, you are creating a diverse habitat and beautiful centerpiece.

Bottom Line

Creating features like the keyhole bed take advantage of a piece of land that may otherwise be left fallow and use recycled materials to produce a crop. When we add this into our yard, we are reducing the amount of organic waste, such as table scraps, lawn clippings, and other compost, that would end up in the garbage. We are then turning this waste into nutrients that fuel a planting area that can provide food for your family or generate happiness from the beauty of its assortment of flowers.

As Farrah Schwab explains in Permaculture News: keyhole beds are a “climate-savvy, space-saving, nutrient-recycling and waste-upcycling method.” So if you did not know about them, you might want to start making plans for next year’s garden!