A raised flower bed, once you have designed and installed it, can save you a lot of time and trouble. It also does not hurt that it will look nice, as well. One nice thing about designing these beds is that almost anything you think of can be used as a retaining wall. Pressure-treated wood products should be avoided because of the potential for dangerous chemicals to leach into the soil and your plants. Beyond that, however, you can let your imagination roam free.
Measure the area where you want to put your raised flower bed. Use your measuring tape to take precise measurements of all sides so that you can plan accordingly. If you are thinking of using materials that will encroach on your gardening space, decide how much of that space you are willing to give up to your retaining walls.
Sketch the rough shape and measurements of your gardening space and the raised bed's retaining walls on your graph paper. Use the whole sheet so that you have plenty of room to plan.
Consider the placement of your raised bed and what kind of sunlight is available. This will help you to decide what kind of flowers will work best. Try planting in patterns or in contrasting color blocks. For added interest, try choosing flowers that bloom at different times so that something is always in bloom for a longer period of time in your raised flower bed.
Gather the building materials for your raised flower bed. Garden centers and catalogs have kits available that are made of various types of wood, including red cedar. Red cedar ages gracefully by turning silver, is relatively inexpensive and weatherproof, and resists rotting. Some kits are also made of plastic. You can also use paving stones, bricks, cement cinderblocks or even old truck tires stacked up. Keep in mind that some building materials are more environmentally friendly than others.
Assemble the frame of your raised bed. Use the mallet and screwdrivers as necessary to put it together. The exact method will vary based on your building materials. Pour sand into the bottom of the raised bed. This will help to improve drainage. Next, heap soil mix (which will vary by what you decide to plant) and compost into the bed and mix it up thoroughly.
Plant your flowers according to the design you worked out on your graph paper. Place a garden hose in the bed and let it run for a while to water the entire bed. Your raised flower bed will drain very well. Because of this, you will need to be especially careful during hot periods to make sure your flowers have enough water. Raised beds require more water than traditional beds.