Keyhole Gardening Tips

Try this inexpensive, green solution to growing food in drought-prone terrain.
Keyhole garden by Dr. Deb Toman

Keyhole garden by Dr. Deb Toman

Photo by: Image courtesy of Dr. Deb Tolman, www.debtolman.com

Image courtesy of Dr. Deb Tolman, www.debtolman.com

Irrigation and crop rotation are some of the ways farmers and gardeners have addressed drought in arid regions in the past.  But a new method of gardening is proving to be less labor-intensive and more affordable for individuals who grow their own food. A keyhole garden introduces a no-dig, permaculture design in the form of a raised bed with a continual feed at the top for manure, vegetable scraps, paper and other brown and green matter. 

An overhead view of this type of raised bed would look like a large keyhole in a circular plot with easy access to the center basket where vegetable scraps and other green matter containing water are added. Most of the hard work is done by the micro-organisms in the garden which convert the compost to healthy soil.

First introduced in arid African regions by the U.K. organization Send a Cow, keyhole gardening began as a grass roots movement to help poor families develop the skills they needed to grow crops on infertile land. The concept has proven to be so successful that it is now being practiced in areas of the U.S. where droughts are common such as Texas. One of the strongest advocates of keyhole gardening is Deb Tolman, Ph.D., Environmental Scientist and Landscape Designer, and Co-Founder and Director of the Silo Project, a non-profit organization centered on sustainability.

Tolman lives in Clifton, Texas, which now has more than seventy keyhole gardens thanks to her educational outreach and workshops. Tolman is passionate about this new way of growing food, not just because it is a progressive ecological concept for arid climates but for altruistic reasons. "It's for people who can't afford to go buy bags and bags of potting soil," she says. "I'm in it for the process of making compost and being able to make it fast. And being able to make it without any store bought materials if possible. Gardening has to be accessible and more people need to garden because the art of gardening is going fast."

cardboard for compost

cardboard for compost

Photo by: Image courtesy of Dr. Deb Tolman, www.debtolman.com

Image courtesy of Dr. Deb Tolman, www.debtolman.com

Tolman's own recipe for a successful keyhole garden is a ratio of 3:1 in the composition of brown and green material which forms the core garden and breaks down rapidly due to the heat generated by the natural decomposition.

Recommended brown material:

  • Brown or yellow leaves and grass
  • Paper and wood products like phone books, newspapers and twigs
  • Straw
  • Sawdust
  • Dead plants
  • Lint from the dryer or vacuum cleaner debris
  • Lots of cardboard and a small amount of wood ash

Recommended green material: 

  • Kitchen scraps (vegetables, fruits, eggshells)
  • Coffee grinds and tea bags
  • Manure
  • Fresh green grass clippings

There are a variety of recycled or natural materials you can use to construct your raised garden bed in the keyhole style. Broken up concrete, rocks, discarded lumber or plastic can be used to create the horseshoe-shaped bed. Just make sure you build enough room in the keyhole to easily access the central basket which can be constructed from chicken wire and should be 1 foot in diameter, 3 feet from the outside wall, and 1 foot higher than the finished height of the outer wall that is 6 feel in diameter.

More on Keyhole Gardens

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A Drought Tolerant Garden

Keyhole gardens are the stars of a new grass roots agrarian movement that allows gardeners to grow food successfully by creating a raised garden with the no-dig, layering concept of a lasagna garden and recycled materials instead of soil. The pictured garden has a center compost basket that distributes nutrients and water to the surrounding garden bed and is accessible by a keyhole notch opening in the circular design.

Photo By: Image courtesy of Dr. Deb Tolman, www.debtolman.com

Brown Matter

The raised bed is created by layering cardboard, paper, dead plants and other brown material on top of each other. All of this will break down over a 30 day or more period and become the "soil" for the garden.

Photo By: Image courtesy of Dr. Deb Tolman, www.debtolman.com

The All-Important Center Basket

All of these recycled materials (straw, cardboard, paper, cloth layered with green matter) will form the base and height of the raised bed and be fed through the center basket whose primary purpose is to distribute water and food (which is 90 to 95 percent water). That water, through capillary action, osmosis and gravity feed, travels out into the garden, accelerates micro-organism activity and "cooks" the layers of recycled matter.

Photo By: Image courtesy of Dr. Deb Tolman, www.debtolman.com

Halfway to Greener Pastures

Here is a keyhole garden in mid-construction with an outer wall constructed from recycled concrete and the beginning of a center basket for nutrient distribution. The surrounding interior will be filled with recycled, biodegradable material like cardboard, sawdust and phone books which, when combined with green matter, will serve as food for the micro-organisms, which in turn will produce nutrients for the plants.

Photo By: Image courtesy of Dr. Deb Tolman, www.debtolman.com

Green Goodness

This recently completed keyhole garden displays the first signs of young vegetable plants sprouting up from the compost. Notice the keyhole opening that allows the gardener easy access to the center when green material can be placed at regular intervals along with occasional watering when needed.

Photo By: Image courtesy of Dr. Deb Tolman, www.debtolman.com

Squash Explosion

The compost created by keyhole gardens is so rich and fertile that the gardener may end up being able to produce more than half his or her food supply from it, thus greatly reducing grocery bills.

Photo By: Image courtesy of Dr. Deb Tolman, www.debtolman.com

Rock Steady

Foundations for keyhole gardens can be constructed out of many types of recycled materials so the gardener has free reign to be creative. This circular design is composed of rocks from Marble Falls, Texas.

Photo By: Image courtesy of Dr. Deb Tolman, www.debtolman.com

Cedar Solution

Here is a soon to be completed keyhole garden where the outer wall is made of cedar stays.

Photo By: Image courtesy of Dr. Deb Tolman, www.debtolman.com

The Timber Cone

This completed keyhole garden features a circular wall made up of repurposed landscape timber which gives it a unique look. More importantly, the cone is perfectly constructed, rising one foot higher than the height of the outer wall, allowing for effective water distribution.

Photo By: Image courtesy of Dr. Deb Tolman, www.debtolman.com

Plastic Fantastic

Another design approach for your keyhole garden is to construct the outside wall out of corrugated plastic with metal bracing like these colorful creations.

Photo By: Image courtesy of Dr. Deb Tolman, www.debtolman.com

Anti-Critter Protection

In case you are wondering why scrap pieces of metal line the rim of this Texas keyhole garden, the reason isn't for decorative purposes. The metal collar is actually an effective barrier against armadillos which like to dig in the garden for worms and other insects to eat.

Photo By: Image courtesy of Dr. Deb Tolman, www.debtolman.com

Idolize Your Garden

Who says your keyhole garden has to look like everyone else's? Be creative. Decorate it. Make it a folk art project that also works as a steady food supplier.

Photo By: Image courtesy of Dr. Deb Tolman, www.debtolman.com

Attack of the Killer Tomato Plants

If you are an avid gardener and like to grow your own food, you might want to build more than one keyhole garden so you can devote an entire garden plot to a favorite vegetable like this healthy jungle of tomato plants.

Photo By: Image courtesy of Dr. Deb Tolman, www.debtolman.com

Despite the dry, desert-like weather of North Central Texas, Tolman has been able to grow an abundance of fresh vegetables like kale, chard, Malabar spinach, tomatoes, carrots and berries and drastically reduce her grocery bill. What she grows changes with the seasons and she produces 70 percent of what she eats. Other members of her community are doing the same.

"To be able to turn a big cardboard pile into compost in a month, that's huge," Tolman states. "I've never been able to keep myself in enough compost but now I won't do anything unless it has composting underneath it. The last one I did was a keyhole garden with plexiglass and that is huge because you see that the four week time period is really a function of the root systems on the top where before I thought it was composting from the bottom up. It's really composting from the top down. And if you construct the keyhole garden in the winter, you've got an instant heated greenhouse."

For more detailed instructions on how to build a keyhole garden you can refer to Dr. Deb's Field Guide or DVD and for instructions on how to care for it you can refer to this article on the Texas Co-Op Power website.

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