Dr. T. Ombrello - UCC Biology Department

GARDEN DAHLIA

Common names: Dahlia, Garden Dahlia

Scientific name: Dahlia hybrid.

While some people refer to garden dahlias as Dahlia pinnata, this really is not accurate since all modern dahlias are hybrids between species. The most common hybrids are the products of crossing Dahlia coccinea with Dahlia pinnata.

Explanation of scientific name:

Dahlia - Commemorates the Swedish botanist Andreas Dahl (1751-1789), a pupil of Linnaeus.

Dahlias have a long history of use in horticulture, earning a well-deserved reputation as consistent bloomers. Enhancing gardens and adorning arrangements as cut flowers, the Dahlia has been acclaimed "Queen of the Autumn Garden" by its admirers. Like many garden flowers, dahlias have fallen in and out of fashion over their 200 years of cultivation, starting with seeds sent by Vincente Cervantes of the Botanic Garden of Mexico City to Abbe Cavanilles of the Royal Gardens at Madrid in 1789.

As members of the large Sunflower family of plants (Asteraceae), dahlias are closely related to chrysanthemums, daisies, marigolds, zinnias, and dandelions. Few genera can match the diversity dahlias exhibit. There are at least 27 species and literally thousands of cultivars developed through hybridization. Heights range from several inches to over 20 feet for some wild species. Flowers come in almost every color imaginable and can be thumbnail size to 12 inches across, blooming from mid-summer until a frost in our area. Flower shapes are also quite diverse, ranging from marigold-like to sunflower-like. The American Dahlia Society recognizes 12 groups of cultivars, distinguished primary by their flowers.

In their native habitat, extending from Mexico to Columbia, dahlias are perennials that develop large tuberous roots to store food for the next growing season. The roots are so significant that Andreas Dahl tried to popularize them as an alternative to potatoes for food. They were used to an extent in France and along the Mediterranean coast, but their peculiar flavor limited their adoption. Napoleon's first wife, Princess Josephine, appreciated the beauty of their flowers and grew them extensively in the gardens at Malmaison, France. Dahlias became quite fashionable and sought after. By the mid-19th century they were a mainstay of many landscapes. In 1850 a dealer in New York was offering over 300 named varieties. In the early 20th century dahlias were a favorite of Monet in his garden at Giverny, France.

As ornamental plants today, dahlias are grown in one of three ways.

	Short cultivars, for use in gardens as bedding plants for a single season, are grown each year from seeds. Seed grown plants, however, are quite variable with irregular sizes, shapes, colors, and timing of blooms. They also aren't very heat tolerant.
	The cultivars grown from tubers tend to be quite large, producing exhibition-sized flowers. They often need support stakes to hold them up. In our area the tubers are dug up in the fall and stored dormant in a slightly moist medium at temperatures between 30 and 50 degrees F. They can be planted back into the garden the following spring.
	A third method of growing dahlias, from cuttings, has become more popular as of late. Dahlias grown from cuttings are selections from seed grown populations that through vegetative propagation (cloning) are quite uniform. They are used as bedding plants in gardens and as potted plants.