Dahlias are showy plants. They can come in many sizes, from 1 foot to 6 feet tall, and have flowers that range from 2 inches to over 12 inches in diameter. They come in many colors and shapes, including daisy-like spheres, multi-petalled spheres, and jagged ruffles. Dahlias are members of the Asteraceae family, which also includes daisies, sunflowers, chrysanthemums, and zinnias.