Keyhole Garden Build

Keyhole Garden partially filled

This week’s project was a keyhole garden. It is modeled after a design created several years ago by a nonprofit organization, Send a Cow, to help families in arid regions of Africa. The design is basically a raised bed with a compost pile in the middle. It holds water because of all the organic matter with which it is filled, and allows greater density of planting because of the richness of the soil.

I learned how to make raised bed keyhole gardens when I attended a workshop taught by Dr. Deb Tolman, an environmental scientist, and a strong advocate for this type of bed.

First, I accumulated 92 landscape blocks, the ones used to build retaining walls. They are more attractive than concrete blocks that can be used. However, this bed will be out in front of my house, so I want it to be attractive. Otherwise, concrete blocks can be painted for aesthetic purposes.

I had plenty of cardboard from boxes I’d used in moving. I removed tape, and burst them into single sheets. I then laid them in a roughly 8′ x 8′ square, with cardboard overlapping by 6″ and then doubled that thickness with another layer of cardboard. On the cardboard, I marked out a 6′ diameter circle, and started placing blocks around on the marks.

Cardboard laid, circle marked, and setting out blocks

I adjusted the blocks around the circle, and aligned the “v” that makes it a keyhole.

First, base round laid out

It is critical to layout the first round carefully, because all subsequent rounds are based on the base round. The second round is placed off-center block by block of the first round. The picture at the top of this blog post is the finished wall. Note that a cylinder of wire (chicken wire or hardware cloth) with a diameter of approximately 18″ is placed upright at the apex of the “V”. This wire cylinder is to contain compostable materials on an ongoing basis.

Watering is done through the cylinder once the garden is filled and planted. In this way, the water goes through the compost and out to the plant roots. The dimensions of the garden (maximum 6′ in diameter) is the maximum distance that the water will migrate out to the plants. Note also that the cylinder is at the center of the circle.

The garden is now being filled by (1) branches and cuttings from bushes on the property; (2) leaves collected from curbs in the neighborhood; (3) wood chips; (4) turf removed when I planted trees; (5) vegetable matter that my neighbor removed when cleaning out her flower beds; and (6) some compost. I will continue to fill the bed, letting rain pack down the contents, adding some dog hair from my folks’ dog brushings, more compost, more leaves, straw, wood chips, and finally a layer of compost and top soil to bring it ready to plant – projected around May 1.

Stay tuned for progress reports!

Building a New Way….in Community Gardens

I was musing yesterday as I was visiting a budding community garden. Most follow the model of outlining beds using timber and then filling in with soil. Sometimes there is a compost pile and compost and mulch are applied sparingly. What if there is another model that is yet to be implemented which is water-wise and drought tolerant? Much like the beds I saw (and posted a picture of them) in the southern Dallas county garden – outlined with logs from the property, filled with mulch several inches deep and with ollas for watering. What if hugelkultur beds became the norm – like a community garden in Plano is working toward? Or keyhole gardens? or other techniques borrowed from drought-stricken areas around the world? If we are to continue to install gardens for the community – and promote and practice farming in the city – then we need to think outside the box as water restrictions become the norm rather than the unusual.

hugelkultur bed

Hugelkultur comes from Eastern Europe, and mimics the forest floor – with wood then twigs then leaves then grasses, all of which compost and then dirt on top.  As the wood deteriorates, it creates a rich environment for the micro-organisms and fungi that are necessary for drawing nutrients from the soil and making them available to plants.  Also, as the wood deteriorates it becomes spongy and holds water.  The net result is that a hugelkultur bed, once established, needs much less watering than a traditional garden bed.  A great reference from a pioneer in the refinement of this technique is “Sepp Holzer’s Permaculture: A Practical Guide to Small-Scale, Integrative Farming and Gardening.”


The keyhole garden technique was developed by nonprofits working in dry-land Africa. The goal was to create a garden bed that would grow the maximum amount of food crops for families with a minimum of water. It is essentially a compost pile within a wall.  Once the bed is established, the central wire cylinder is the place that compost (kitchen scraps and other compostables) is placed, and any watering that is done is in the cylinder.  The moisture is then pulled out into the soil where the roots are as it is needed.  A structure of bent PVC pipe creates a framework to support either shade cloth, to protect plants from searing summer sun, or poly to extend the growing season from early spring to late fall and possibly through the winter here in North Texas.  Dr. Deb Tolman, from whom I learned the technique, says that you start with a dumpster load of cardboard that goes into the garden, along with piles and piles of leaves, newspaper, food scraps, manure, old cotton t-shirts, straw, grass clippings, and anything else that is compost-pile fodder.  These are carefully moistened as they are stomped down and compressed before additional layers are added.  Then the whole thing is topped by compost and top-soil.  And planted.  Building a keyhole can be a group party – with a large group, once the wall is built, it only takes about 2 hours from start to planting!

One important advantage of a keyhole garden is that it is perfect for someone who cannot bend over to weed or plant, yet wants to continue to garden.  It’s a raised bed extraordinaire!

Contact me if you want a hugelkultur bed or a keyhole garden to be part of your gardening experience this year!