Few gardeners are lucky enough to have perfect conditions for growing vegetables right off the bat. The most common challenge is poor soil quality, especially in urban and suburban areas where topsoil has been removed and compacted during construction. That’s why raised garden beds are such a popular solution since you’re literally rising above the natural terrain – and obstacles -- to growing healthy plants.
Depending on how high you go, tending raised garden beds can also be a lot easier on your back and can even make gardening accessible from a wheelchair. The idea is to stand or kneel in the paths when working in the raised beds
Another major advantage compared to a traditional garden plot is being able to produce in small spaces and focus your attention and resources on a more defined area. Your watering, fertilizing and pest control will be limited to the growth area instead of wasted on walkways. The soil also stays more productive because it’s not compacted by footsteps and warms up earlier in the spring.
On the downside, you’ll invest more upfront labor and budget getting a raised garden bed built and prepped. But once you’ve got the structure and soil in place, your garden will be easier to maintain for years to come. Here’s how to build a raised garden bed.
Choose your spot
Since vegetables are most productive when planted in full sun, your ideal spot will be free of shade. The next best choice would be a place that gets four to six hours of direct sunlight a day, with most of that in the morning hours. Try to locate your garden bed away from trees if possible so tree roots won’t compete with your vegetables for water and nutrients. You’ll also want good access to water, since raised beds will dry out more quickly, requiring more frequent watering than traditional gardens.
How much space will you need to build raised garden beds? That depends on the size of your design and ambition. Read on.
Map Out Your Raised Garden Bed Design
Since building and starting even a small raised bed garden involves time and expense, you can save both by thinking through each part before you buy any materials or plants. Guide the planning and design for your raised garden bed based on a combination of these factors:
- Stooping and reaching: How easy do you want to make tending your plants? For some gardeners, this is the main consideration. Raised garden beds are usually 2- to 4-feet in maximum width, so you can easily access all plants inside the bed from the perimeter. Height is usually at least 6 to 8 inches, but many go higher to accommodate root depth and relieve back strain. If you build a frame that reaches slightly below waist level (28 to 30 inches high), you’ll be able to work and harvest your bounty without much bending, or even reach comfortably from a wheelchair. Keep in mind that will take a lot of material, plus a lot of dirt to fill that space. While you can make the bed as long as you want, you may be tempted to walk across your bed if it’s too long. Allow room for an outer path on each side of the bed that’s 2- to 4-feet wide to allow easy access with tools and equipment like wheelbarrows, hose reels, chairs or stools, and wheelchairs.
- Your appetite and climate: What fruits and vegetables do you and your family like to eat? Start with what you like and then narrow down the list based on what grows best in your climate. If you’re not sure, ask for help at your local gardening center or county extension service.
- Plant spread and height: How much space will your plants need at maturity, including root depth? It helps to select more compact or bush-type plant varieties and focus on vegetables with relatively shallow roots. For example, arugula, tomatoes, broccoli, cabbage, endive, garlic, bok choy, lettuce, onions and spinach have roots 12 to 18 inches long. Small fruit crops such as strawberries, blueberries, blackberries and raspberries are also good choices for raised beds. Keep in mind that since there’s no barrier at the bottom of a raised bed, more deep-rooted vegetables may grow beyond the organic soil into your existing soil, where they can potentially absorb contaminants and lose their organic status. If the underlying soil is contaminated by toxins, make the raised bed tall enough to keep roots thriving in organic soil.
- Building Materials: What type of frame works best? Untreated wood is recommended for organic gardening, so woods that are naturally resistant to decay such as cedar, redwood and black locust will last longer. Other options are bricks and flagstone, or even large river rocks if you add a liner to hold the soil in place. Avoid concrete blocks, though, because they can contain toxins that can leach into your soil.
- Time and treasure: What will your budget and schedule allow? The idea of having a raised garden bed high enough to avoid stooping and bending may be very appealing, but the cost in materials, soil and labor to build won’t be insignificant. You’ll also want to think about how much time you have for maintaining your garden. It may be a good idea to start with a small raised bed and plan to build more beds as time and resources allow.
Creating healthy organic soil
Whether your soil is too sandy, full of clay, compacted, or contaminated by toxins, you can overcome any dirty problem by creating your own ideal soil conditions in your raised bed garden. It’s best to start with a soil test to find out if you need to start fresh to avoid toxins or if your soil just needs help. You can save money by just adding organic amendments such as compost and organic fertilizers to improve your soil’s texture or fix the acidity and nutrient balance. If you’re planning to purchase organic soil or other amendments be sure to look for the Organic Materials Review Institute (OMRI) certification on the product. You can make a good soil mix for raised beds with equal parts of garden soil, organic matter (compost, peat moss, composted manure), and porous material such as vermiculite or perlite, according to the University of Maine Cooperative Extension Service. If you don’t have good quality garden soil you can substitute more organic matter.
Planting for success
You may choose to plant in rows within the bed or simply group similar plants together by maturation time or height. Keep in mind that nature rewards plant diversity with more beneficial insects and microorganisms in the planting area. On the other hand, monoculture -- or grouping the same type of crops together – can lead to more pest and disease issues. You can increase productivity by planning and planting for multiple seasons and paying close attention to crop timing. You can also increase garden intensity by growing vertically to save space. Stake or cage tomato plants and train vine crops like cucumber and squash on a trellis.
Mulch and water to maintain
A multi-purpose activity, mulching helps keep soil moist and roots cool in summer while controlling weeds and erosion. After you’re done planting, consider adding newspaper or cardboard for additional weed control before applying a 2- to 3-inch-deep layer of bark or pine mulch around the base of the plants. Since raised beds are more prone to drying out than in-ground gardens they need at least 1 inch of rainfall or irrigation per week for healthy growth. Drip or soaker hose irrigation is best because it focuses water on the root system instead of the entire plant.
Fight insects and disease:
Raised bed gardens have no magical immunity to pests and disease, but the accessibility can make it easier to win the battle. Your first lines of defense are promoting healthy growth through proper mulching and watering and keeping a lookout for signs of infestation. Check under leaves for insect eggs and destroy them before they hatch. Bring in some recruits by attracting beneficial insects like lady beetles, lacewings and predatory wasps with companion plants in and around your raised beds. Good options include dill, fennel, coriander, Golden Alexanders, yarrow, sunflowers and goldenrods.
For fast action, you can choose organic products for disease and insect control -- just be sure to look for the OMRI label for organic gardening, like you'll find on many EARTH’S ALLY products. On the insect front, EARTH'S ALLY® Insect Control uses a blend of rosemary, clove and peppermint oils to treat and control spider mites, whiteflies, aphids, thrips, mealy bugs, leaf rollers and scale insects. A broad-spectrum fungicide and bactericide, EARTH'S ALLY® Disease Control extracts oils from thyme to treat and control powdery mildew, black spot, botrytis, blight, wilt, blossom end rot, damping off, leaf curl and leaf spot.
Ready to get started with a diy raised garden bed? Find more details and videos on raised garden beds from the University of Maine Cooperative Extension Service or your local extension service.