Dahlia - Cultivation

Cultivation

In 1846 the Caledonia Horticultural Society of Edinburgh, offered a prize of 2,000 pounds to the first person producing a blue dahlia. The color has never been produced. While dahlias produce anthocyanin, an element necessary for color production, to achieve a true blue color in a plant, the anthocyanin delphinidin needs six hydroxyl groups. To date dahlias have only developed five, so the closest that breeders have come to achieving a "blue" specimin are variations of mauve, purples and lilac hues.

Dahlias grow naturally in climates which do not experience frost (the tubers are hardy to USDA Zone 8), consequently they are not adapted to withstand sub-zero temperatures. However their tuberous nature enables them to survive periods of dormancy, and this characteristic means that gardeners in temperate climates with frosts can grow dahlias successfully, provided the tubers are lifted from the ground and stored in cool yet frost-free conditions during the winter. Planting the tubers quite deep (10 – 15 cm) also provides some protection. When in active growth, modern dahlia hybrids perform most successfully in well-watered yet free-draining soils, in situations receiving plenty of sunlight. Taller cultivars usually require some form of staking as they grow, and all garden dahlias need deadheading regularly, once flowering commences.

To date, 99 dahlia cultivars have gained the Royal Horticultural Society's Award of Garden Merit, including:-

• "Bednall beauty"
• "Bishop of Llandaff"
• "Clair de lune"
• "David Howard"
• "Ellen Huston"
• "Fascination"
• "Gallery art deco"
• "Gallery Art Nouveau"
• "Glorie van Heemstede"
• "Honka"
• "Moonfire"
• "Twyning's after eight"