Native to Mexico and Central America, dahlias are tuberous rooted perennials in the aster (Asteraceae) family. Years after its discovery, the first dahlia was taken to Europe. Although it adapted well to European soils, it did not dependably survive winters. In the 19th century, botanists in the Netherlands began to experiment, and from a pair of dahlias came the majority of dahlias found for sale today.
In terms of its genetics, the dahlia is a marvel. It is said to have more genes affecting the blossoms’ appearance than most other flowering plants, giving it one of the most versatile flowers on the market today.
Hybrids in commerce today are available in a very large number of flower shapes, sizes and colors (except blue). Plants generally bloom from mid-summer to fall in colors that include red, pink, lavender, purple, orange, yellow, white, and parti-colored. Newly developed hybrids include variations of a hue within a single blossom. Varieties grow from 1.5′–6’ tall. In an attempt to create order from chaos, hybrid dahlias have been organized into ten different bloom classifications or groups: single, anemone, collarette, waterlily, decorative, fall, pompon, cactus, semi-cactus and miscellaneous.
Dahlias can be high maintenance plants requiring a large investment of time to grow well. Smaller varieties are excellent container plants which must also be overwintered in a frost-free location. Tuberous roots must either be lifted in fall, or heavily mulched for protection from frost. Potential diseases include viruses, crown gall, root rot, wilts and powdery mildew. Aphids, caterpillars and leafhoppers are somewhat common insect visitors. Notwithstanding, dahlias are excellent in borders, window boxes and containers. Dahlias make an excellent cut flower.
A new collection of dahlias has recently been added to the English Garden at the Idaho Botanical Garden. Dahlias may also be found blooming in the Meditation Garden and elsewhere on the grounds.
Written by IBG gardener, Paul Rodgers.