Raised garden beds allow you to build up the perfect soil, and they usually contain fewer weeds than garden beds that were dug from former sod. Since working in raised beds does not require as much bending and stooping, they are easier on the back and knees, and raised beds can be built for people with disabilities.
Make gardening in raised beds even easier by planting low maintenance flowers. Of course, all gardens will still require some work.
Plant hardy perennial flowers. Unlike annuals, which die at the end of every growing season and must be replanted in the spring, perennials will live for several years, and they often spread and maintain their population with little help from you. Make sure the perennials you choose are hardy for your area and won't be killed by winter frosts.
Some easy perennials to consider are Siberian squill (Scilla siberica), daylilies (Hemerocallis spp.), black-eyed Susans (Rudbeckia serotina), blazing star (Liatris spp.), purple coneflower (Echinacea purpurea) and New England aster (Aster novae-angliae). Growing perennials from seed or bulb will be cheaper, but transplants will need less maintenance and will provide more immediate results.
Consider growing native plants. Native wildflowers and grass are perfectly adapted to the local climate, and they provide food and shelter for songbirds, butterflies and other wildlife. Some wildflowers native to North America include butterfly milkweed (Asclepias tuberosa), Canada anemone (Anemone canadensis), prairie smoke (Geum triflorum), harebells (Campanula rotundifloroa), wild strawberry (Fragaria spp.) and Solomon's seal (Polygonatum spp.).
A good field guide or a native plants nursery can help you determine what flowers are native to your region. Native plants tend to have extensive root systems, so your raised bed should be open on the bottom so that the plants can reach into the ground underneath. Many native wildflowers will thrive in regular garden soil.
Buy large, healthy plants. While small or sickly plants may be cheaper, they will need more babying to get them to establish themselves and thrive in your raised bed. Plants that are healthy from the start will need less attention from you and will fill in the bed more quickly.
Plant the flowers close together. Nature abhors bare soil and will quickly fill it in with weeds. Planting your flowers closely together might result in smaller plants, but will also offer fewer opportunities for weeds to move in.
Water your raised bed with a soaker hose. Soaker hoses are more efficient than sprinklers, and you can leave a soaker hose in your raised bed throughout the growing season---or all year in regions that don't freeze. With a soaker hose, all you need to do to water your flowers is turn the spigot.