Dahlias are perennial flowering plants native to Mexico. They bloom in mid- to late summer in a variety of shapes, colors and sizes. A bed of dahlias, planted en masse, presents a striking focal point in the summer garden. For these types of plantings, choose cultivars that grow 12 to 24 inches high to avoid having to stake them. Plant the dahlia tubers when the soil warms to at least 60 degrees Fahrenheit.
Choose a sunny location in which to plant the dahlia bed. If you live in an area that gets particularly hot sun, provide the dahlias with afternoon shade.
Mix 5 to 6 inches of compost into the top 12 inches of soil. Rake the dahlia bed until it is level and smooth.
Use a gardening trowel to dig planting holes at a depth of twice the length of the tubers. Space them 18 to 24 inches apart, depending upon the size of the cultivar. Rows should be spaced 3 to 5 feet apart.
Place each dahlia tuber in the holes with the eye (on the ridge, where the tuber joined the stem) facing up. Cover with soil.
Water the dahlia bed only if the weather has been particularly dry. Depending upon variety, the dahlias should begin to sprout within six weeks.