According to the American Dahlia Society, there is a plethora of dahlia colors and forms. They address them in three groups according to purpose—garden type dahlias, dahlias for cutting and border or container dahlias.

Official dahlia classification identifies them by flower form, here are the different types:

• Cactus dahlias
• Decorative dahlias
• Ball dahlias
• Pompon dahlias
• Single dahlias
• Mignon dahlias
• Semi-double dahlias
• Collarette dahlias
• Anemone dahlias
• Orchid dahlias
• Peony dahlias
• Waterlily dahlias
• Stellar dahlias

Flower size is another factor that varies between dahlia types. Some are 2 inches or less, while others are 10 inches or more. The dahlias with the largest flowers are often referred to as dinner plate or giant dahlias. The popular 'Cafe au Lait' is a dinner plate dahlia.

Other popular dahlias include types that are especially tall (5+ feet), types that are early blooming and types with dark foliage.

Learn how to grow dahlias.