Raised bed gardening can be a solution for a number of gardening problems with the additional benefit of giving you more control over growing conditions. Some of the many reasons to consider raised garden beds include: better drainage, less soil compaction, elimination of root competition from trees, fewer weeds, and the ability to control soil quality, texture and acidity. Even if you have a bad back or sore knees, raised garden beds can make gardening more pleasurable and more accessible. Follow these tips and tricks to get your organic raised garden bed started.
Raised Garden Beds vs. Planter Boxes
While planter boxes are self-contained with solid sides and a bottom, raised garden beds have sides but no bottom, and they are placed directly on the soil. Planter boxes work best for plants with shallow roots. Raised garden beds allow plants with deeper roots to grow past the depth of the bed. This is worth considering when growing vegetables or other edible plants in areas with contaminated soil, including many urban gardens.
Planning Your Organic Raised Garden
Before building your raised beds, answer these questions for best results:
- Where do you want to place your raised beds? What length and width will be large enough while being easy to work around? Raised beds that are too high can be tough to work with.
- How much full sun will each raised bed get per day? If you want to grow vegetables, make sure that the bed gets at least 6 hours of full sun per day. Do your research so you plant the right flowers, fruits, and vegetables in the right conditions.
- What do you want to grow in each bed? Vegetables? Companion plants to deter pests? Perennials, including native plants that attract beneficial insects? Consider how large each plant will grow over time and allot enough room in the raised beds.
- How tall do you want the raised beds to be? Shallow beds are easiest to build but will require you to kneel and bend while gardening. Shallow beds will not be best for deep-rooted plants and are problematic if the underlying native soil is contaminated.
- What materials will you use to build the frame? Cedar is a popular framing material and is safe for growing vegetables. Treated lumber should be avoided for any organic raised bed. Steer clear of materials like concrete, too—they may leach into your soil and alter soil acidity.
Organic Soil and Raised Beds
You might decide to fill your raised garden bed with purchased soil, compost and amendments. If you decide to go in this direction, buy organic soil and organic compost from a reliable source. The OMRI (Organic Materials Review Institute) certification on the product is your best assurance that the material is organic. Note that such products can be hard to find, but are worth seeking out.
Most gardeners use their existing soil in raised beds, adding organic amendments such as compost and organic fertilizers when needed. A step that is frequently missed is doing a soil test to determine the basics of existing soil. Soil texture, soil acidity, soil nutrient deficiencies or overabundance, and soil contaminants, like lead and other heavy metals, can be determined by soil tests.
Different plants require different soil and site conditions. For example, if you want to grow blueberries, acidic soil is critical to success. Most vegetables like more alkaline soil. Inexpensive soil tests are easily done through your local agriculture extension—check online for details.
Organic Vegetable Gardening in Raised Beds
Consider the root depth of the vegetables you want to grow in an organic raised bed. Many vegetables have shallow roots—arugula, broccoli, cabbage, endive, garlic, bok choy, lettuce, onions, potatoes, and spinach typically have roots that are 12 inches to 18 inches in depth. Other vegetables have much deeper roots—asparagus, lima beans, okra, parsnips, pumpkins, winter squash, sweet potatoes, tomatoes, and watermelon can send roots down two to three feet.
Buy or build raised garden beds that accommodate plant roots as much as possible while ensuring that the height of the raised beds is comfortable for you to garden in. Since there is no bottom to a raised bed, more deeply-rooted vegetables may grow past the soil into your native, existing soil. Keep this in mind if the underlying soil is contaminated by heavy metals or other toxins.
Choosing Organic Seeds and Plants
An organic raised bed garden starts with organic soil and organic plants. If you decide to start your plants from seed, there are many choices of organic seeds. It's easy to find organic vegetable and annual seeds, but a bit harder to find organic perennial seeds.
To track down organic perennial seeds, look to online and local native plant nurseries. Local native plant societies often have a list of plant resources on their websites.
Buying certified organic live plants can be a bit of a challenge. It is very expensive for nurseries to get an organic certification. Be prepared to pay more for organic plants in your garden, just as you pay more for organic vegetables when grocery shopping.
Using Beneficial Insects in Your Beds
Pests are a reality in any garden. Keep your raised beds organic while minimizing plant damage by attracting nature's pest control—beneficial insects like lady beetles, lacewings, and predatory wasps. Include companion plants in and around your raised beds that attract these beneficial insects. Dill, fennel, coriander, Golden Alexanders, yarrow, sunflowers, and goldenrods are just a few of these useful plants.