“You don’t have to bend over so far,” says Coco, Tangipahoa Parish county agent and horticulturist with the LSU AgCenter. “That’s the advantage to me.”
Good advice for we gardeners of a certain age. But there are many other reasons for elevating plants. Raised beds keep the soil in place and make weed control easier. They create attractive divisions and visual elements in a landscape, and conceal unsightly features such as faucets and central air-conditioning units. Built high enough, they can discourage dogs and other animals from turning the flowerbed into a favored stomping ground. And for New Orleans-area residents who don’t relish the thought of digging around in soil that sat for weeks in floodwaters—or consuming vegetables grown in it—raised beds provide a renewed, controllable environment.
Most important, raised beds provide good drainage in these swampy climes. “That’s the number one reason you make raised beds,” Coco says.
Where to put them:
If it’s growing vegetables and herbs you have in mind, choose a spot that gets lots of sun. Shadier spots are good for many flowers and bedding plants. Leave some space between raised beds and buildings, however, so the container doesn’t interfere with termite control, or make it more difficult to reach rooflines and gutters.
Materials to use:
Just about anything that will hold soil can be used to build raised beds, Coco says. Railroad ties are a popular and attractive method, but choose older, weathered ties; newer ones contain chemicals that could leach into the soil. More readily available, and easier to lug around, are treated wooden landscaping timbers sold in lumber stores and garden shops. (In my native rural East Texas, where neighborhood association restrictions are as rare as vegetarian restaurants, many people favor used tractor tires, but we won’t go into that.)
Coco has put together an instruction sheet for do-it-yourselfers. (For the complete document, with photos, call the Tangipahoa county extension office at 985/748-9381.) Twelve 8-foot landscaping timbers are sufficient for one 4-foot-by-8-foot bed stacked four timbers high. Cut four of the timbers in half; arrange the timbers in a rectangle with the corners overlapping, log cabin style. With a long 5/8-inch drill bit, drill two holes at each corner six to eight inches in, so that 1/2-inch (wide) metal rods can be inserted vertically through all four timbers. It will take roughly 1 1/3 cubic yards of soil to fill the container.
Filling it in:
If placing the container over a lawn, Coco recommends spreading a layer of leaves to kill any grass before filling in the soil. If the raised bed is less than a foot tall, she adds, gardeners should dig out enough topsoil to reach a depth of 12 inches. Fill the bed with a mixture of soil and organic matter like compost or leaves; finish it off with a thin layer of bark or pine straw mulch.
What to plant: Flowers, vegetables, shrubs and even trees can thrive in raised beds; indeed, some trees that are difficult to grow in South Louisiana, where the water table is high, do much better in raised beds. “If somebody in New Orleans really wanted to grow a peach tree, I would recommend a raised bed for that, since it requires good drainage,” Coco says. “Or if they needed a dogwood for some reason.”
The soil in a raised bed will subside over time, and needs to be replenished periodically. As for fertilizer, Coco recommends levels somewhere between what would be required for ground plantings and what you would use in potted plants. The same goes for water: raised beds don’t dry out as quickly as pots, but typically need to be watered more often than ground-level beds. A “soaker” hose, cut into 25-foot sections and looped three times, is the perfect size for a 4-foot-by-8-foot bed. •