Keyhole gardening- the key to saving water
By Carolyn B. Edwards BCC Staff Writer
Master Gardener Diane Sellers read an article about keyhole gardening in an issue of Texas Co-op Power magazine last year and thought it sounded like the perfect way to garden in the Hill Country.
"The concept was developed by a charity organization working in Africa in an area where they got little rain, had lots of rocks and very little soil," she said. "Does that sound familiar?"
Over 20 people in attendance at the January meeting of the Madrona Garden Club agreed with chuckles.
Keyhole gardening involves building a circular raised bed garden that has an opening going to the center, like a slice taken out of a pie. In the center is a wire tower where the gardener tosses in compostible materials and water. The raised bed is filled with materials like cardboard, newspapers, anything that's not synthetic. Those materials are then topped with a 10-12 inch layer of good garden soil, seeds are planted, plants are mulched and the garden is good to go!
"I did my keyhole garden with the help of my husband and my grandson," said Sellers. "And of course I used professional tools - a piece of rope and a screwdriver to lay it out."
The best size for a keyhole garden is no more than six feet across. Sellers used the rope and screwdriver to mark her circle, then spray painted the outline.
Next came the heavy lifting, the part where the grandson came in really handy. Using rocks from their property, they began building the wall to follow the contours of the outline, using brick mortar, until the wall was about waist high. "It doesn't have to look beautiful," said Sellers, although she confessed to adding a little bling to her garden by sticking old keys and jewelry into the mortar here and there.
Once the wall was up, she fashioned a tube about one foot across out of chicken wire and about a foot taller than the wall. The tube was placed in the center of the bed, with a mound of stones at the bottom for drainage. She tied light cardboard around the tube to keep the soil from falling into it.
"The cardboard liner will quickly rot away, but by that time the roots of your plants will be holding the soil," she said.
Then she began the layering of materials, "making the lasagna." Sellers used lots of cardboard, newspapers, some horse manure, even some old T-shirts and jeans.
"It takes a lot of material to fill it up," she said. Sellers said she even did some dumpster diving to collect enough cardboard and was thrilled one day to find bags of shredded paper someone had tossed in the trash!
She recommends soaking the cardboard and paper products in something like a water-filled wheelbarrow to make it easier to handle inside the garden walls.
This lasagna needs to be packed down thoroughly to within about a foot of the top of the wall.
Once the lasagna, which will eventually become soil, was packed into the walled enclosure, Sellers dumped about a foot of good garden soil on top and her garden was ready to plant.
"Our cats decided we had built them the world's biggest litter box," she said. "So we had to make a fence." They used stakes and chicken wire to make sections of light weight fence that were easy to remove to access the garden.
While Sellers used rocks found on her property, keyhole gardens can be made of a variety of materials, including concrete blocks, bamboo, short pieces of landscape timbers, and cedar stays. It's now possible to purchase kits for building a keyhole as well. They cost around $200 and are easy to set up. One gardener even created a mini-keyhole in an old wheelbarrow.
Some keyholers use rebar or PVC pipe to create the support for a cover to provide some shade in the summer or protection from freezing.
Sellers said there are a lot of good reasons for Hill Country residents to try keyhole gardening. The system uses less water than a conventional garden. Seedlings can be watered with a sprinkler, but once plants are established, water is poured into the central tube. It uses up kitchen scraps by composting in the tube. The design of having water and compost in the center gets nutrients to the roots quickly.
"You get a large return in a small space," Sellers said.
Keyhole gardens are easy to protect against the weather, easy to mulch and harvest. The soil doesn't erode and the gardens are easy to maintain.
For Sellers, one of the biggest pluses is enjoying the comfort of gardening while standing up. "Your back will thank you!" she said.
Anyone thinking about trying the method should realize that starting a keyhole garden can require considerable labor in the beginning. A keyhole can also be relatively expensive, depending on your construction materials. Some people think they look intrusive in the landscape, but again, that depends on what materials you use to build, and how careful or skilled you are with rock laying, for instance.
For most gardeners, a lushly green plot of tasty veggies or glorious flowers would overcome any tendency toward the eyesore category.
As the lasagna breaks down into soil, the gardener will have to add more garden soil, or add more lasagna between plantings.
There are lots of resources online for more information about keyhole gardening, including a video on youtube.
As the drought continues throughout the Hill Country, it's good to know there is a way to have fresh vegetables and flowers using very little water.
"When you conserve water, you conserve life," said Sellers.