Dahlias can be either annuals or perennials. According to the University of Nebraska-Lincoln Cooperative Extension, dahlias that flower the first year from seed are annuals, while you usually grow perennial dahlias from tuberous roots.
Dahlias are members of the sunflower family of plants (Asteraceae). Dahlias include at least 27 species and thousands of cultivars (cultivated varieties) developed through hybridisation, according to the Union County College Biology Department. The flowers come in almost every colour, and size of the flowers range from tiny to 12 inches across.
Types of Dahlias
Single-flowering dahlias have one row of petals, usually grow to a height of no more than 3 feet and have flowers that are 4 inches or less in diameter. Examples of single-flowering dahlias include orchid-flowering, anemone and collarettes. Double-flowering dahlias have multiple rows of petals, grow taller and have larger flowers.
You can grow dahlias from seed, from tuberous roots or from cuttings. Dahlias are hybrid flowers, which means that plants grown from seeds are not consistent. Dahlias prefer full sun and well-drained soil.