What do I put on the bottom of a raised garden bed? Design your raised bed garden layout to maximize sunlight and layer with a ground cloth, limestone, sand, organic matter, and garden soil.
Gardening in raised beds requires less equipment compared with traditional in-ground methods and offers a more controlled growing environment. In a raised bed, you can add, supplement, and monitor the exact soil and nutrient combinations each plant requires, as well as adjust the water intake more easily than in traditional farming. We talked to the gardening experts at The Farm at Okefenokee near Folkston, Georgia, for their tips on getting started with raised beds.
Raised Garden Bed Dimensions
- Height. Use the natural width of a board, or double or triple up the boards, up to 14 inches. Those with limited mobility might prefer their raised beds to be waist-high to reduce back or leg strain.
Raised beds that are too short run the risk of making the middle of the bed less accessible. Most raised beds at The Farm are 10 by 5 by 1 feet. “They’re beautiful,” Bob Hawkins, the regenerative agriculture farm manager, says. “But if they were taller, it’d be easier to reach the middle.” As a result, the workers at The Farm grow plants that have a longer growing time in the middle of those beds, since their location makes them relatively difficult to access. - Length. Hawkins notes that the size of your boards will typically decide the length of your raised beds. He recommends a maximum length of 10 feet to help with watering the beds. “You can separate the watering and irrigation for each plant so it’s easier to control,” he says.
- Spacing. Nicole Pramik, who’s responsible for the greenhouses and nearly 100 acres of crops and gardens on The Farm, avoids planting mints, thyme, or oregano in raised beds that are close together, since she finds that those plants are prone to unwanted spread. I’ve similarly found these plants to be a problem in places without a long winter. She also cautions against the raised beds being too close together in the first place, which allows for easy access plus less seed drop from mature plants in adjacent beds.
- Sunlight. Hawkins recommends building your raised beds from north to south for both sides to have equal amounts of sunlight. “If you have a plant that isn’t going to do as well in full sun and likes fewer hours of direct sunlight or partial shade, then you could run it east to west and have the larger plant that loves full sun on the south side and the shaded-out plant on the north,” he explains.
You can also create microclimates within a bed. “Trellising can help with that,” Pramik adds. “Trellises can provide afternoon shade, depending on where they’re placed.” - Width. Keep the width of your raised beds no more than 4 to 5 feet wide, Hawkins says, and ensure that at least three sides of the raised bed are accessible. The middle of L-shaped raised beds can be difficult to access without stepping in the beds, which will compress the soil. Tip: Keep a spare board to lay across your raised beds to step on instead of compacting your soil!
Eastern Red Cedar Boards
Eastern red cedar, well-known for being resistant to mold and insects, is the material of choice for most of the raised beds at The Farm. Workers at The Farm are optimistic that the beds will last for at least five years and hopefully closer to 10.
The wood for these beds isn’t stained, which Hawkins likes, but you could use boiled vegetable oil. Staining, however, isn’t necessary for red cedar. Other people may prefer metal panels, other woods, or whatever is available for their raised beds.
Raised Garden Bed Soil Layers
After the wooden frames have been built, the workers add a ground cloth to the sides and bottom. Then, they layer in limestone, followed by sand, organic matter, garden soil, and decomposed pine bark on top. This arrangement of substrate will nourish the soil microbes, which in turn feed the plants. Additionally, the workers add ClimateGard, which is a 4-4-4 fertilizer, to the raised beds. ClimateGard has some Bacillus spp. and Trichoderma spp., which help reduce harmful bacteria and fungi in the soil.
All layers except the sand and limestone are mixed in wheelbarrows prior to filling the bed. The Farm sources its organic matter from its huge compost piles of a variety of animal manure, greens, and browns.
“The sand keeps the organic matter from getting trapped in the rocks with the water and going anaerobic. A layer of sand keeps it from rotting in the bottom,” Hawkins says.
As part of The Farm’s commitment to regenerative agriculture, it implements a system of soil regeneration. Instead of using heavy, nutrient-concentrated soil, throwing it away afterward, and then replacing it with new soil, The Farm promotes a living soil method. The soil feeds the crops and, in return, the excess leaves and roots of healthy crops will be composted for use in future beds. Biochar will also be implemented. While some soil amendments are currently being brought into the system, The Farm’s goal is to be able to generate all of its own soil accoutrements.
Adjust Soil and Rotate Crops
As The Farm learns through experiments on these raised beds, its workers are hoping to get two or three growing seasons out of each bed before they’ll have to adjust the soil. In south Georgia, they can plant frost-tolerant greens in winter, tomatoes and peppers in spring, and then in fall, brassica greens and even mushrooms. They’re also considering small berries.
Hawkins recommends you track what you plant in your raised beds, not only for the purposes of companion planting, but also to reduce the likelihood of grouping together plants that are detrimental to each other.
Saprophytic organisms that feed on decaying organic material, such as fungi and soil bacteria, will need some time between growing cycles, Hawkins notes. For example, if you’ve grown peppers in your raised bed for six months, you could probably plant them again for another six months, but then you’ll want to switch it up for beans and, later, carrots. If you don’t rotate your crops, you’ll risk them becoming more susceptible to disease.
Make It Your Own
Raised beds are a wonderful addition to any landscape. By following these tips, you’ll be able to customize your own raised beds that’ll last for years to come.
Kenny Coogan earned a master’s degree in global sustainability and co-hosts the “Mother Earth News and Friends” podcast. He also created and hosts the TV show Florida’s Flora and Fauna with Conservationist Kenny Coogan.
Originally published in the June/July 2025 issue of MOTHER EARTH NEWS and regularly vetted for accuracy.
