Building a keyhole garden is a great way to grow a low-maintenance garden in a small amount of space! Here’s how to do it…

I had never heard of a keyhole garden until recently, but I find the idea very intriguing – especially the low-maintenance aspect and space-saving features!

A keyhole garden is a round, raised garden concept with a compost feature in the center. It is called a “keyhole” garden due to its unique shape, with a path to the center that makes the entire garden bed easily accessible.

Here’s the basic shape of a keyhole garden:

This is a great garden idea for those with limited garden space, and it also makes a lovely feature for the center of a larger garden, or for a courtyard or small backyard. Its height is easy on your back, and makes the garden more accessible for those who have trouble getting up and down, and the compost feature in the center provides an ongoing source of nutrients while giving you an easy way to feed your garden with organic compost without needing a traditional compost pile.

You will need an area that gets plenty of sun, and is large enough to comfortably fit a 8-10 foot diameter raised bed. It doesn’t need to have good soil – or even any soil at all, so you can use this garden method in areas with bad soil, or even on a patio or concrete pad.

You can construct your keyhole garden out of a variety of materials of your choosing – anything from bricks to stones, to metal, cinderblocks, or cedar logs will work fine – depending on your preferences. Just make sure you are using materials that are not treated with chemicals that could leach into the soil if you plan on growing food crops. A good choice for the compost tower in the center is wire mesh or a piece of old fencing, but you can also use whatever you prefer for this as well.

Since the garden is raised quite high off the ground, you will want to choose low-growing plants for this style of garden. Otherwise, what plants you grow are up to you – just make sure they are well-suited for the amount of sun your garden will receive.

Here are 5 basic steps for building your own keyhole garden, from EcoHome.net:

1.) Create your circle by staking the middle of the area and using a string the length of the circle radius to mark the outer edges for your build; or you can just eyeball it if you prefer. Either way, somehow create a visual circle on which to begin construction.

Construction of the garden will be a layered affair and should end up with a slight angle sloping out from the center, for drainage and nutrient delivery. Therefore, each layer adds to the mound in the center.

2.) To begin, create the compost tower. Again, you can use any kind of mesh or fencing, you can even create a square with four stakes then weave a basket style wall with ropes and reeds. Whatever method you choose, my advice would be to keep it simple and use materials that you have easy access to. Once the center tower has been built, fill the bottom of it with fist-sized rocks for drainage. This will be the centre of your garden and the highest point from which your bed will slope, so create a generous mound.

3.) On top of that you can add medium-sized chunks of organic matter that will provide both nutrients and moisture as they break down. The rest of the compost tower can be filled with anything else you would put into your garden compost…

4.) Once the outer walls have been marked and the center compost basket is constructed, you can begin to fill the raised bed with the “lasagna” method. A layer of cardboard at the bottom will prevent any weeds or grass from growing through from the soil below. The second layer needs to provide drainage, this can be done by scattering fist-sized rocks or other materials such as broken terra cotta pots.

The next layer can include wood chunks, branches, twigs, ash for potassium, soil and grasses. The layer after that should feature lots of soil, and if you so choose, aged manure. Fresh manure should never be used as it will burn the plants. Each layer should slope slightly from the inner tower to the outer circle.

5.) As the layers begin to grow, build the outer wall to contain them until you reach the desired height for your raised bed. Many keyhole gardens stand as much as 3 feet tall, which offers a nice break for your back during maintenance and harvest!

Here is an example keyhole garden layout, plus a cross-section view:

Image Source: Fix.com Blog

You can expect your keyhole garden to last at least 5 years – perhaps longer if you use durable materials and add compost regularly to maintain the soil. Once the walls start to break down, it’s time to take it apart and re-build.