Nothing beats a dahlia for summer color. Growing these varied, spiky flowers is like having a box of garden crayons at your disposal. The flowers form on branching, fleshy stems or open in solitary splendor on the bedding-plant types in mid- to late summer. Several different flower categories, from the petite mignonettes to the gigantic dinner-plate dahlias, offer possibilities for any space.Expert dahlia growers recommend pinching off the first crop of side flower buds to encourage vigorous plant branching and larger flowers in peak season. All dahlias are fodder for brilliant seasonal cut bouquets and are always one of the most popular cut flowers at local farmer's markets. Their blooming season extends into fall and is only halted by the first frost.Gardeners in climates colder than Zone 8 should cut back the withered foliage after the first frost and dig up tubers to store over winter. For a fast start with dahlia plants before it's safe to plant outdoors, pot the tubers up, water sparingly and grow in a sunny location until sprouts appear, and then transplant outdoors after the last frost.