Dahlia in full bloom.
image by Martinclay/sxc.hu
A perennial flower, dahlias produce large flowers in nearly any color imaginable, except for blue and true yellow. They return year after year to grace your borders and garden beds. Dahlias grow on long stems, making them well-suited to cut flower arrangements. Pruning is necessary to encourage large blooms, otherwise you will be left with many small imperfect blooms and a top-heavy plant. The process of pruning dahlias is disbudding, which is the careful removal of buds that interfere with large flower growth. It must be done the entire blooming season for best effect.
Top the central bud of the dahlia plant in early summer to encourage blooming. Pinch-grasp the bud on the the top of the main stem between your thumb and forefinger and remove it from the stem. This encourages lateral stems to grow from the central stem.
Examine the buds on the end of each lateral stem. There are three to four buds on each stem with one on the tip of the stem and the others around the sides. Pinch off the side buds, leaving the central bud in place.
Deadhead spent blooms to encourage further blooming. Cut off the spent flower directly below the nearest leaf node to where the new growth is.
Remove the leaves along the stem at the bottom of the plant so there are no leaves touching the soil. This combats mites and keeps the plant healthy.
Lop the dahlia in late autumn after the foliage begins to brown and die back. Use sharp shears and leave the central stem at least 4 to 6 inches high, removing any lateral stems below this height.