The first “room” in my backyard plan was made up of seven raised beds. I didn’t understand agriscape design (elegant edible landscaping) at the time. I just knew I wanted to grow healthier food.
I played around with gardening a bit over the years, but I became serious about growing my own foods seven years ago when I moved into a foreclosed home that had a backyard moonscape. I read everything I could get my hands on, attended classes and seminars and spent a lot of time on YouTube.
There is one caveat to YouTube. Just because it is on YouTube or social media, it doesn’t mean that it is true. Always check out what you are viewing or reading for consensus among other gardeners and experts.
From the start, I went for raised gardens after doing my research. Let’s get real about Southwestern soil. It is great soil for cactus and desert-adapted plants, but other than that, it is a very frustrating experience for new and experienced gardeners alike. That’s why cacti are the only plants that grow naturally here!
When you make an investment of time, labor and money, you want a great yield. Raised beds versus in-ground gardening give you a better chance of doing so.
Raised beds cure a large list of gardening ills but they do cost a bit more from the start. If you are resourceful, however, you can build most raised gardens with little or no cost.
You might be surprised at how many types of raised beds exist. Most are friendly to arid gardens. I will address the following raised bed styles:
— Traditional construction with cedar, stone, brick
— Hugelkultur: raised hills using small logs and twigs as a base
— Keyhole: African-based raised bed with an internal compost bin
— Zuni Waffle Garden: ground level “raised garden” used by Southwestern Native Americans
— Hay bales: Temporary raised garden using hay both as a structure and compost
The traditional wood, stone, concrete block or brick raised bed is what most people picture when you mention raised gardens. They each have pluses and minuses. Whenever you can, look for recycled materials or clearance items for your structure. Your expense should be in quality soil, not your structure materials. The structure doesn’t create your high-yield garden except that it allows you to use high-quality controlled soil instead of native soil.
A great place to find cheap recycled materials is Habitat for Humanity’s ReStore shops. Click on the link and enter your ZIP code to find one near you.
THE RAISED BED SIZE
Dimensions: The length of your bed doesn’t matter. That is really controlled by where you will place it. Most people create 4’, 6’ or 8’ beds in length. The important dimension is width. You want to be able to reach across to the middle of the bed comfortably if you can walk around the bed. This way, you can reach all plants. If the bed is against a structure, build it one-arm’s-length from the structure because you can only reach it from one side. One of the main points of a raised bed is that you don’t compact the soil by walking on it as in a traditional garden, so don’t build it so you have to climb in. That may sound strange, but I have seen people do it. Your reach is usually half your height so a 4’ width is comfortable for just about everyone if you can get to all sides of the bed. Plan for everyone who will be helping in the garden. If you have little ones, either plan the width to their needs or just keep what they are growing on the ends of the beds where they can reach from three directions.
Depth: You need enough room in a raised bed so that whatever you grow has room for roots plus at least 4” below it (for water drainage). For example, standard carrots will grow to be 8” so a 12” raised bed just makes it. Tomato and pepper plant roots like 12”. I wouldn’t plant them in a raised bed less than 18” deep. You also won’t want to fill your soil all of the way to the top because you will add nutrients, compost and mulch (more about that when we talk about soil) on top of the soil. So you will need a 4-6” clearance at the top. Mine are 18” tall and the tomato and pepper plants love them. I dug down about 6” below the surface, inset the dig about 6 inches from the edge of the raised bed (so that the bed has a solid surface to rest on) then built the 18” raised bed. It gave me 24” depth total. People wonder why my tomato plants grow so thick and tall with so many fruits. Their roots aren’t starved for nutrients and space. By digging, I also saved myself some money in supplies for a higher bed and 18” is a great height to sit on to work on the garden. If you dig as I did, remove that soil. With a raised bed, you need quality, nutrient-controlled soil and you won’t get that from your native soil usually.
Design: The shape doesn’t matter as long as you can access every inch of your garden from the outside. I have seen some incredible designs with uses of triangles, circles, U-shapes and L-shapes. Design your raised beds so they enhance the beauty of your yard and not take away from it. Even if you are using recycled materials, you can make your gardens look wonderful. I love Houzz.com for ideas. The direct link for raised beds is http://www.houzz.com/photos/query/raised-vegetable-garden-beds/nqrwns
WOOD RAISED BEDS
The wood raised bed is easy to build and relatively inexpensive. Cedar is the best wood to use but it is also the most expensive initially. In the long run, you will get your money’s worth because it will last much longer than other products. Cedar beds will last 5-8 years while other woods will begin to deteriorate after about three years. Whatever wood you choose, don’t use treated wood. The most prolific treated woods are railroad ties and most palettes. You can find some palettes that aren’t treated but check the stamps on the wood before you decide to use it.
Cedar or redwood UNTREATED 2”x6”X8’ plank average cost: $10 (life as a raised bed 5-10 years)
Fir or pine UNTREATED 2”x6”X8’ plank average cost: $5 (life as a raised bed 2-5 years)
You will need to waterproof the sides of your wood. Many people use black plastic to do so but if you do, don’t put it on the floor of the bed. You want worms to get up into your soil and water to wick away from it. Plastic on the bottom of a raised bed causes water to pool at the bottom and blocks off worms. Soggy roots encourage disease and rot.
There’s also a great product, Eco Wood Treatment, that will cost you more than black plastic but it protects your wood from rot and stops fungus and mold from growing, which are detrimental to your vegetables. The product is non-toxic, safe for edible plants and pets and toddlers who like to put everything into their mouths. I had one of those! I still have a dog who eats vegetables and chews on a piece of wood if it chipped off from the side of a raised bed. The wood treatment can be painted on with a brush, sprayed on or you can soak the wood to treat it. Its only ingredients are crushed minerals, so it is very eco-friendly. Home Depot and Amazon carry it. If you use a non-toxic sealant like this, you will extend the life of your bed. Please make sure that it is non-toxic and eco-friendly, however. Anything else can make you ill.
You can buy raised bed kits. Just make sure that the wood and materials are high quality. Most are only 8-12” tall, so you will have to buy 2-3 to stack on one another unless you are willing to dig down about 12”.
ROCK, BRICK OR CONCRETE
I have these three together because even if you use natural rock for your bed, to hold it together and waterproof it, you will probably have to use concrete. The opinion differs as to whether or not concrete is toxic. The concrete dust that occurs during demolition and the process to create blocks are toxic. The dust will not affect you as you use the blocks unless you cut them and breathe in the dust (when cutting, use a mask then hose off the block before you add it to your bed. The dust can cause lung irritation and in rare occasions, more serious complications. In its block form, very little dust is present. Most expert gardeners believe that with care, the blocks should be safe.
Concrete blocks and brick are easy to install, cheap and you can often stack them a couple of rows high without adhering them together. I was new to raised bed construction so I consulted an organic garden landscaper. I cemented block together then stuccoed the exterior and sealed the interior with a non-toxic waterproofing product called Drylok 27512 Latex Water Proofer. Make sure that you purchase the right Drylok product because the company carries many types, including those that aren’t guaranteed to be non-toxic. Concrete blocks will last much longer than wood, but if the ongoing discussion over concrete blocks worries you, build with wood.
Rock walls are beautiful and natural but you may have problems locating enough rock that fits your needs and you have no other options other than cement so you don’t lose water in the crevices. If you are willing to put in the effort, however, you can build a beautiful section of your garden.
I am not going to give you step-by-step instructions for the beds but I do need to discuss some key points. A photo above offers a diagram of typical wood bed construction.
I already addressed waterproofing for wood and concrete beds, but there are other steps important to all types of beds.
Gophers, moles and any burrowing “varmint”: I live in Queen Creek, AZ and the area is known for the large gatherings of gophers, especially when one gopher shouts “food!” and digs a tunnel toward it. I always place hardware cloth at the base of my raised beds and fold it up the sides. If you are using wood beds, staple it to the sides. If you are using concrete or stone, go about 6″ up the side and fold it as tightly as you can against the rock or block. Hardware cloth looks like chicken wire but it is much thicker and the space between the wires is tighter. I use 1/2″ hardware cloth.
Weeds and grass: Even though you are in a raised bed, weed seeds may still reside below in the native soil. Also, if you have built your bed on a lawn, you will need to kill the lawn underneath. Lay down thick cardboard at the bottom of your bed overlapping each piece about 8-12″. Landscape cloth works also but it won’t deteriorate like cardboard, so it will block worms and won’t add nutrients to the soil. Worms love deteriorating cardboard, so you will send out an invitation by using it. Wet it down to start the process. I also throw in some crumpled newspaper at this point. If you are blocking grass, lay down about 6 inches of straw or dried leaves. I use straw because it is less likely to contain seeds, unlike hay. Although hay is more nutrient rich, you will be plucking long hay “weeds” from your garden if you use it. Wet the newspaper, straw or leaves. This begins the decomposition process. Weeds and grass won’t grow without sun and air. The cardboard starves the weeds and grass of both. The decomposition process turns them into beneficial nutrients and decomposition raises the temperature, thus “burning” the weed seeds.
Low tunnels: Low tunnels are simply PVC arches that make it easy to shade your veggies from the sun, warm them in the winter with winter garden blankets, sheets, etc., use thick plastic to warm up transplants and seeds right after planting and hang bird netting to keep birds from your tomatoes and berries. The three techniques let you start growing earlier, extend your growing time at the end and winterize some plants so that rather than plant new ones, you can reuse your past season’s and give the plants a head start in the next season. This works well for strawberries but not all plants will produce well again.
In another blog, I’ll show you how to construct low tunnels, but I am including a photo of my tunnels and a YouTube video of a similar low-tunnel construction in case you want to get started right away.
A great YouTube video shows you one way to create the low tunnels.
Raised Bed Soil: Now place your soil mixture into the bed. If you want to use a custom premium mix, see the recipe in the blog that preceded this. If you want to start simple first, a high-quality raised bed soil and compost (not composted mulch) provide your garden with a good start. Raised bed soil is what you purchase, not potting soil or garden soil. Also, don’t mix in your native soil.
Mulch and fertilizer: Once you plant your transplants, place 3-4″ mulch around them. Straw is excellent for raised beds and since you may have purchased it for the layering (called lasagna gardening), it’s free. Don’t push the straw right up to the stems, however. It can cause disease or rot. Leave about 2″ open. The mulch is so important for water conservation and to keep plants warmer in cool months and cooler in warm months. It also acts as a dry base on top so that fruit won’t lay on the wet soil. Don’t place mulch on beds where you are growing seeds until the seedlings are 2-3″ high. The seedlings need the sun to grow and mulch might impede that.
Give your plants fertilizer right away. I love to use fish emulsion (linked YouTube video) and alternate it with compost tea (when I don’t have compost to make it at home, I just by “Bloom,” which is a commercial compost tea concentrate. For those of you in my area, you can buy it at Ewing Irrigation on Ocotillo east of Crismon). I mix the fish emulsion mix with 2 TBSP fish emulsion to one gallon of water and pour about one cup at the roots of each transplant and feed the plants every 2-3 weeks. You don’t have to use these fertilizers but I think you will see the difference.