Little lion's heads, or dinner-plate-sized blooms that rival the sunflower's girth, the dahlia represents one of the most beloved fall bulb bloomers. Popular cut flowers for arrangements as well as for lasting fall color in the garden, dahlias are available in an extensive variety of colors, sizes and shapes.
Dahlias are available in a plethora of color selections. Standard warm hues of red, orange and white are common, as are white, lavender and pink. Contemporary cultivars include blue purple as well as a deep purple, near black hue. From these basic colors, dahlias then take a leap into fanciful combinations of shades with stripes, blends, bi-colors and variegations.
The American Dahlia Society recognizes no fewer than 20 different forms of the dahlia flower. Ranging from bunchy heads full of petal layers to single rings of daisy-like petals, dahlias have a surprising array of different shapes to provide interest in your fall garden. The tiny pompom is just as the name indicates, a tightly packed, small ball of inward curving petals. The double cactus has a more spidery-looking form, with fingery petals that reach toward the center of the flower. Collarette and single blooms have one ring of petals around a large center, while the double formal has numerous layers of petals.
Double and single cactus forms tend to be some of the largest dahlias available. Almand Supreme is a lovely, bright yellow single cactus form that will grow to be over 10 inches in diameter, as will Fidalgo White Mafolie, also a single cactus with creamy white petals and flecks of yellow at the interior. Cabo Bella, a striking cactus-like form but with lanced tips giving the overall impression of a firework, has white petals with deep pink edges. Catherine's Cupid is a perfect ball of pink petals, while Silver Tips is a tiny 2-inch pompom with two-toned purple and white, fully curved petals.
Dahlias are grown from tubers, or bulb-like, fleshy structures that are planted in early spring in order to bloom that late summer and fall season. Prepare the bed by adding a layer of organic compost, such as manure or pine bark, and work it into the soil to a depth of 10 inches. This practice improves drainage and provides nutrients for the tuber. Plant the tuber in a hole 3 to 4 inches deep, on its side or horizontal with the shoot facing up. Cover with soil and keep moist, but do not allow the area to become soggy.
If you place a garden stake next to the tuber, marked with the cultivar name and other important information at the time of planting, you will have the added benefit of using the stake to tie off the quickly growing dahlia for support. Many dahlias will reach sunflower-like proportions but with a much more delicate stalk, and blooms that heavy will require support so they don't buckle or bend as the grow. Pinching off blooms as the dahlia plant grows will create fewer, larger specimens.
Store dahlia tubers after the first hard frost in the late fall. Cut back the dry foliage at this time. Use a garden spade to lift the tubers carefully from the ground. Rinse the soil from them and allow them to dry for at least 24 hours. Store with the shoot end facing down packed in sphagnum moss in a box. Place the box in a dry, cool place not warmer than 55 degrees Fahrenheit.