Once in place, a cactus bed makes an easy no-fuss garden because cacti do not require as much water or maintenance as other plants. The downside is that contact with cactus spines can be extremely painful, so you should not choose this type of bed if you have young children or pets. Also, although cacti generally grow well in Mediterranean-style climates, wet winters can cause problems if your soil is heavy. To compensate, make sure your cactus bed has excellent drainage, which can best be achieved by making it a raised bed.
Raising the Bed
First, you will need to decide what material to use for the walls of your raised bed. Large rocks about 15 inches (32.5 cm) high, outlining an irregularly shaped area, will provide a natural look. You can also surround the bed with large and rot-resistant cedar or redwood logs. Whatever material you choose, make sure the bed's walls are at least 15 inches (32.5 cm) deep.
Where Cactus Grow Best
Select a site on a sunny slope south or west of a building for the best drainage, and spade up the ground to a depth of 1 foot (30 cm) beneath where you plan to build the bed. Fill the area with gravel after removing the soil from that top 1 foot (30 cm). Arrange whatever materials you use for the bed's walls to surround the area now packed with gravel. Once the walls are up, shovel into space between them, to a depth of 1 foot (30 cm), a mix containing 1 part soil, 1 part sharp sand, and 1 part gravel or pumice.
Always wear heavy leather gloves when planting cacti. If you find the gloves are not heavy enough, wrap them with duct tape to make them more spine-resistant. You can also use tongs to move the spiny plants, or sheathe them in heavy material, such as an old throw rug or tarp when shifting them. Choose various cacti, including giant Saguaro (Carnegiea gigantea), which grows in USDA plant hardiness zones 9 through 11, Opuntias, whose hardiness varies from USDA zones 5 through 12, and Mammillarias, which grow in USDA zones 9 through 11. Your garden will look more interesting if you intersperse the cacti with succulents that enjoy similarly dry conditions, such as Yuccas, which grow in USDA zones 4 through 12, and Agaves, which grow in USDA zones 8 through 12. After planting the cacti in the soil mix, water them and mulch them with 2 inches (5 cm) of pea-sized gravel.
You will need to water cacti more frequently while they become established. During the first four to six weeks, water them once per week. Then, switch to watering them only once every two weeks from spring to fall. In fall, stop watering your cacti until the following spring. Cacti in the ground do not generally need fertilizer. However, if you prefer to give them some, you can feed them once every two weeks from spring to fall with a low-nitrogen, water-soluble cactus fertilizer, such as 1-7-6, using one teaspoon per one gallon of water.