Dahlias are native to Mexico and Central America and today's garden varieties are mostly hydbrids. There are over 2,000 individual varieties available commercially and more than 12,000 dahlia varieties in all. There is certainly a dahlia for all. The size of dahlia blossoms ranges from a miniature pompon half-inch in diameter to a huge variety that can grow up to 15 inches across. The plants themselves range from 18 inches to 7 feet tall. This highly cultivated plant is bred for improved colors and sizes and for foliage color and quality. A new trend today is to develop dwarf and semi-dwarf varieties that do not need stalking.
Dahlias are classified by their flower type, including single, anemone, colorette, waterlily, decorative, ball, pompon, cactus, orchid, peony and stellar forms. Dahlias are very useful because they can be incorporated into almost any sunny summer border with a wide range of perennials, annuals and flowering shrubs.
Dahlias grow from tubers which can be purchased in spring. The tubers are taken up in the fall and packed in sand, garden loam, or peat and are stored indoors. Dahlias are most easily propagated by dividing the tubers. In the very early spring, when the new shoots begin to show, separate the clumps with a sharp, sterilized knife. They prefer moist, organic, wee-drained soil and full sun to produce the most quality flowers, so add a generous amount of compost and low-nitrogen fertilizer to the planting hole. Plant tubers of larger varieties up to 6 inches deep and shorter varieties, 2 to 3 inches deep. Spacing should be 1 to 3 feet apart. Dahlias are greedy: feed with a 10-20-20 or similar fertilizer every 4 to 6 weeks during the growing season. Always water the day before fertilizing. Periodically apply foliar applications of a water-soluble fertilizer.
- New York & New Jersey Getting Started Garden Guide: Grow the Best Flowers, Shrubs, Trees, Vines & Groundcovers.
- The Michigan Gardening Guide. Jerry Minnich
- Carolinas Getting Started Garden Guide. Toby Bost