A winding, raised perennial bed unifies the landscape and anchors your home. Many raised flower gardens become living works of art, using plants to change through the seasons. Even raised vegetable beds are gentler on the gardener's back and make weeding quick work. Although they add elegance and creativity to a yard, raised beds also require planning and structure.
Contractors commonly scrape the yards of newly constructed homes bare of valuable topsoil, leaving nutrient-deficient subsoil behind. Even well-tended yards develop soil deficiencies after years of supporting plant growth. Raised beds overcome these problems and compensate for naturally poor soils. They also deter pests, add character to the landscape and support dense plantings. In fact, the Penn State Cooperative Extension reported that a raised bed yielded double the harvest of a traditional garden.
Plan raised beds in a sunny location, beyond the drip line of existing trees or shrubs. When choosing the location of a raised bed, mark the outline with garden hose or twine. Notice the amount of sun the potential bed receives throughout the day, any drainage issues and heat-reflecting surfaces like brick walls or fences. Live with the tentative plan for a few days, moving the lines until settling on a final design. Remember that mowers have difficulty with sharp curves. Multiple small curves appear busy and unprofessional.
Keep the purpose of the bed in mind when creating a raised garden. Place the center of a vegetable bed within arm's reach, while sizing perennial beds large enough for mature plants. Remove weeds or grass and spray the area with a wide-spectrum herbicide, if desired. To further smother weeds, cover the area with multiple layers of wet newspaper. Install edging, if necessary, and extra soil. The University of Connecticut Cooperative Extension recommends working 3 inches of compost into the bed before covering it with 2 inches of mulch. Don't worry if young perennial plants look lost in new beds; fill in the bare areas with inexpensive, temporary annuals for quick impact.
Beds 6 inches high or less do not need support, according to the Purdue University Extension. However, rain and watering eventually erode higher, unsupported beds. River rock, cement pavers, pressurized lumber and plastic borders are common materials, but don't limit yourself. Creative gardeners use upended bottles, zig-zagging bricks or cylindrical post sections in staggered heights. Edging maintenance varies; grass grows quickly between rocks and pavers while lengths of landscape timbers suppress invading grass. Set any edging at least 2 inches deep to block grass rhizomes from the bed. Don't use railroad ties, used tires or treated lumber to edge vegetable beds because these materials may leach harmful chemicals into the soil.
Never build a new raised bed around established shrubs or trees. Adding mounds of soil over the existing plant's root zone smothers the surface roots and starves the plant. The soil buildup around the trunk of the tree also encourages rot, and fungal infections may enter fruit trees through cracks in a buried grafting bud. In addition, avoid locating raised beds around wooden structures or up against houses because the moisture in the soil rots exposed wood and encourages insect damage.