This attractive dahlia is putting on a display of blooms in front of the Palm House.
The genus Dahlia comprises 30 species of tuberous perennials which have given rise to over 20,000 cultivars. All of these species originate from Mexico and Central America, where they grow in mountainous areas. Members of the genus have hollow stems and usually pinnate, toothed leaves. The species are simple in their single flowers, and extensive breeding has given rise to a range of flower forms, including pompom, ball, colorette, cactus and waterlily, which vary greatly in size and colour. Dahlia merckii is a Mexican species, whose tubers produce wiry, branched stems to 2m in height, which are clothed in pinnate foliage. The single flowers are 8cm in diameter, and the ray florets vary in colour from white to purple, and the central disc florets can be purple or yellow. Flowers can be borne singly or in racemes. This species will over-winter in the garden if grown in a warm, sunny site.