Non-traditional, drought tolerant raised beds

I love to experiment in my garden so I have an area that is very flexible where I can try out different techniques. The west side of my backyard is my normal garden, a set of seven raised beds. The center is an edible circle and entertainment area. The eastside is my experimentation area, or “playground.” Currently, I have a keyhole garden and Three-Sisters mounds, which are part of a Zuni Waffle Garden. Soon I’ll be planting a Moringa Tree as an experiment. It is the most nutritious tree on the earth. Watch for a future blog on that one!

Now onto two non-traditional gardens that are successful in the Southwest.

KEYHOLE GARDEN
The Keyhole Garden was developed by the Southern Africa Food Security Emergency (C-SAFE). It was developed originally to help AIDS/HIV patients get enough nutrients through fresh foods not easily available to them. It uses little water so that even in areas where water has to be hauled or it rains infrequently, it is easy to irrigate. The garden uses scraps of food and plant garbage as nutrients, the walls are raised so it is easy to use for those who can’t bend easily to tend a traditional garden, and the rock or brick sides allow a person to sit on it. It is 5-6 feet wide so everything is within reach. A compost bin resides at the center of the structure so compost tea is automatically fed into the soil.

I appreciate the conveniences (and so does my back) this innovation offers. The garden is built using the Lasagna Technique, so everything needed for good soil was available for free. The technique is explained below. The original garden was designed to use rocks or local wood so that the African gardeners could use free, accessible materials to build the structure. Use whatever structure you would like. I used retaining wall block.

The Keyhole Garden looks like an old-fashioned keyhole if you were to see it from above. It is a circle with a wedge cut out at one point and a small circle that rests at the tip of the wedge. The wedge allows you to step up to the compost bin to place compost materials and to water the garden through the bin. A picture of mine and a graphic are below.

MyKeyholeGarden1   Let’s build
The structure: Mark a 5-6 foot circle in a sunny place in your yard. A great way to do this is to take a piece of rebar, pound it into the ground in the center of where you want your circle, attach string that is 2.5 or 3-feet long and use landscape spray paint to mark it out while holding the string. Spray paint in a wedge that is wide enough to let you step into the center of the circle (about 3 feet at its widest point). Landscape paint is easier because you can hold the can upside down.

Now keep the rebar in place and cut the string to about 9 inches long, then trace the 18-inch circle around it. This will be your compost bin. The wedge cutaway will extend from the outer wall to the edge of the compost bin.

At this point, you can decide to build directly on the ground or dig down a little bit for a stronger base for your walls. Since I used retaining wall blocks, I dug down a few inches and put in some sand  where the blocks would rest so I could make everything level and make the wall stronger. Build your wall to 18-24” high. Remember to build in the wedge. I also used Landscape 500 silicone under the top block layer to hold everything together.

If you want to lay down hardware cloth, put it  into the floor of the circle now. It protects your garden from burrowing animals that could eat your produce. Lay it flat inside the circle and around the wedge then fold up excess upward against the walls so that the animals can’t get in through the sides.
Now build your compost bin. I use the same hardware wire but you can use chicken wire, bound sticks, bamboo – anything that will create a cylinder, won’t deteriorate and will let water flow through it. Place it inside the circle at the point of the wedge. Use rebar or sticks pushed into the ground to stabilize it.

KeyholeGarden__GRAPHIC_t837Your soil (Lasagna Garden Technique): Place a couple of layers of flattened cardboard into the bottom of the garden. IMPORTANT: As you do the next steps, pile the soil ingredients around the compost bin a bit higher than your walls so that as you water through the compost bin, the water will naturally flow downward to the rest of the garden (see the diagram to the left). Stack about 4-6” of twigs in the bottom of the garden and smash them down. You are creating natural drainage. Throw about 6-8” of crumpled newspaper and dried leaves or straw on top. Water the layers. Finish off with about 6-8” of compost and again apply water. Water twice a week for 8-12 weeks and let it decompose before planting to create rich soil, or, if you want to plant immediately, add 6-8 inches of raised bed soil and plant. As the ground settles, you will have to add more compost and raised bed soil. Plant larger, water hungry items at the top and smaller plants at the base. This garden is GREAT as a salad garden.

Build the compost bin: Place a pile of rocks with the center higher than the sides into the base of the compost bin. Add a layer of straw or newspaper on top of the rock, put some compost in and then green ingredients (kitchen scraps, green leaves, cuttings from your garden, etc.). You will continue to layer dry ingredients (straw, dry leaves, etc.) and greens when you have them available. Each time you add green or dry ingredients, add a bit of compost to the top. Water your compost enough to keep it moist but not soggy.

Maintenance is easy: Just keep building compost with kitchen scraps and dried materials and water through the bin. I put in a bucket of water a couple of times a week during cool season but I also installed small automatic sprayers up around the bin and turn them on in the summer to offset the arid heat. You can do the same thing without a drip system if you just water the garden with hose two or three times a week.

HUGELKULTUR (pronounced hoogle-culture)
What I love about a Hugelkultur garden (besides the name) is that everything is free and you don’t have to build a structure to use it. This raised garden works off of wood decomposition. Because of that, it is also called a Forest Garden.

I haven’t made one myself but I want to give you as many options as possible. I saw one done at Justin Rohner’s home in Gilbert, AZ, and he removed Bermuda from his yard, rolled it and used it in place of the wood. It took a lot of patience and expertise as an agriscape designer to make it work. He cautions that Bermuda grass has to be torched in order to kill the seeds, so I wouldn’t advise it unless you want Bermuda growing in your bed or you want to use a roofing torch. I can hear some guys getting all excited at the idea! I have used the torch on soil after removing Bermuda and it does work for killing the seeds and small roots but not the pesky rhizomes (underground stems and shoots – my backyard nemesis). So I’m going to tell you how to build a traditional Hugelkultur with wood.

Hugelkultur_0Some people dig a trench, pile in the logs and/or sticks, stack on the native soil and then pile on compost. Others simply build directly onto the ground. You mound up logs, branches and sticks for decomposition and air space (Don’t use pine or walnut. Pine is very acidic and walnut is toxic) then pile compost and soil on top of it so that you have steep mounds or hills. Straw on the sides is recommended to avoid run-off. The decomposition creates rich soil and the wood creates a natural drainage base and nutrients as it rots. Water flows naturally from the top down. The walls should be steep. The average angle is about 45 degrees so that you can easily reach every part of the mound.

It’s good to mound like a plateau at the top rather than make it pointed. That way the water can pool and soak slowly into the ground. You don’t want a run-off situation down the sides. In fact, a  slight indentation at the top will capture rainwater and give you an easy way to water the whole garden. Spray down the sides with water about once or twice a week during the hot summer months. The combination of wood and soil makes it great for water retention but nothing survives our summers without a little help. I have provided a link with more details on how to construct them. If you design it to fit naturally into your yard, it can become a focal point as an elevated area of your garden. Just mix your edibles with some flowers and you will have a wonderful visual mound.

A great video will also help you understand the process through a hugelkultur built by by W.T. Jeffrey at the Glenreynie Gardens and a year-later update on how his beds turned out. His beds are lower than most but it shows you the process. Most beds are about 4 feet high.

In the next blog, I’ll talk about watering. Then later, I’ll cover other non-traditional gardens. Now that you are thinking of raised beds, I think we need to get to the watering issue in arid lands first.

Jknapp

I am a certified agriscape designer and Maricopa County Master Gardener. I have been gardening since I was six years old and worked in my grandfather's garden. I believe that the only way to be a responsible gardener is to garden organically. It improves our soil, is safer for us to eat, sustainable and it protects our pollinators and soil from chemical poisoning.