Some soils and sites are so challenging for perennial gardening that your best option is to elevate the bed above ground level. When you’re faced with a shallow soil over bedrock, put aside your crate of Acme dynamite and compromise by raising the bed.

A raised bed is any planting area in which soil is “raised” above the existing grade a few inches or more. Such beds may have sides of sloping soil, or they may be contained in planter boxes made of wooden frames or low stone walls. Raising a flower bed enables you to deal with salt-affected soils without the time-consuming and often unsuccessful battle of getting the salts out of the soil. In addition, good drainage is absolutely assured in a raised bed, even over hardpan (click here for more) or wet, soggy sites.

Controlling soil quality is simplified in a raised bed. You can choose exactly the right soil for the flowers you plan to grow. Use a good soil mix and fill the planter to within a few inches of the top to keep the soil from washing out. Fewer weed seeds find their way to an elevated surface, and those that do are conveniently within reach.

Raised beds offer many advantages beyond coping with bad soils:

• Providing access for people with disabilities: You can build raised beds to accommodate the needs of the wheelchair-bound or otherwise disabled gardener. The ability to reach the soil surface without having to bend or stoop is also a real help for anyone with back trouble. For even greater comfort, build benches right into the wall surrounding the raised bed, so that you can garden from a seated position. Built-in benches also provide convenient extra seating for guests.
• Correcting property flaws: You can use raised flower beds to break up uninteresting, flat pieces of property. Or terrace steep hillsides with a series of beds defined by short retaining walls and stairs to create more useful and eye-catching spaces.
• Creating barriers: Raised beds make effective barriers, directing traffic patterns around the bed and making it very clear that foot traffic is off limits there. Anywhere that a hedge seems an obvious choice, a raised bed provides a colorful, more solid alternative. Raised beds also add a decorative touch at the edge of walks, driveways, decks, and patios.
• Extending the season: Perennials benefit from raised beds even where soils aren’t a problem. In climates with very short growing seasons, soil in a bed constructed from stone or brick thaws out and warms up faster in spring than soil at ground level. Stone and brick also collect and store heat during the day and slowly release it back into the bed when temperatures fall at night. Plants are thus protected from sudden cold snaps, and the growing season is extended. An extra few weeks can make all the difference in determining whether fall flowers have a long enough season to gather energy for their late show.
• Protecting plants: If you have small children or pets, putting the flowers in a raised planter keeps the flowers safe from casual assault. A single landscape timber is usually high enough to discourage drivers from running over and smashing flowers alongside a driveway, street, or alleyway. For a softening effect, plant flowers with a trailing habit at the edge of the bed so that they can spill out and flow down the sides. Some gardens are completely overrun by gophers, moles, or other burrowing rodents. These furry gourmets enjoy nothing better than a meal of your perennials’ roots. Line the bottom of the planter box with wire mesh to prevent these pests from getting into the soil.  ....read more