WDahlia is a genus of bushy, tuberous, herbaceous perennial plants native to Mexico and Central America. A member of the Asteraceae family of dicotyledonous plants, its garden relatives thus include the sunflower, daisy, chrysanthemum, and zinnia. There are 42 species of dahlia, with hybrids commonly grown as garden plants. Flower forms are variable, with one head per stem; these can be as small as 5 cm (2 in) diameter or up to 30 cm (1 ft). This great variety results from dahlias being octoploids—that is, they have eight sets of homologous chromosomes, whereas most plants have only two. In addition, dahlias also contain many transposons—genetic pieces that move from place to place upon an allele—which contributes to their manifesting such great diversity.
W'Bishop of Llandaff' is a cultivar of the dahlia, a garden plant. It is a branching, tuberous tender perennial with dark purple, almost black, foliage. This produces a stunning contrast with its scarlet flowers. The plant was first bred by Fred Treseder, a Cardiff nurseryman. It was selected by and named to honour Joshua Pritchard Hughes, Bishop of Llandaff, in 1924 and won the RHS Award of Garden Merit in 1928. The plant is about 1 m tall and flowers from June until September. As with all dahlias, frost blackens its foliage, and its tubers need to be overwintered in a dry, frost-free place.
WDahlia coccinea is a species of flowering plant in the daisy family Asteraceae. Its common name is red dahlia, although the flowers can be orange or occasionally yellow, as well as the more common red. The species is native to Mexico but has long been cultivated in other countries for its showy flowers.
WDahlia imperialis, or bell tree dahlia, is an 8-10 metre tall member of flowering plant in the family Asteraceae. It is native to Mexico, Central America and Colombia. It is a plant of the uplands and mountains, occurring at elevations of 1,500–1,700 metres (4,900–5,600 ft), and its leaves are used as a dietary supplement by the Q'eqchi' people of San Pedro Carchá in Alta Verapaz, Guatemala.
WThe following is a list of dahlia cultivars which have gained the Royal Horticultural Society's Award of Garden Merit. They are tuberous perennials, originally from South America, with showy daisy-like composite flowerheads in all shades and combinations of white, yellow, orange, pink and red, flowering in late summer and autumn (fall). Much work has been done on the development of a range of flower shapes and sizes. They may be sold as dry tubers in Spring, and started off in heat before being planted out after all danger of frost has passed. Alternatively they can be purchased later in the season, in pots ready to flower. Dwarf bedding types are usually cultivated as annuals and discarded after flowering. In mild areas without penetrating frosts, mature plants can be overwintered in the garden; otherwise, they are lifted and stored in a frost free place. They are easily propagated from cuttings in Spring.
WDahlia 'Moonfire' is a Dahlia cultivar with very dark, almost black leaves like Dahlia 'Bishop of Llandaff'. It is classified as Group 10 Miscellaneous. The orange-yellow flower heads are 80 mm wide and sit on stems of up to 85 cm height.
WDahlia pinnata is a species in the genus Dahlia, family Asteraceae, with the common name garden dahlia. It is the type species of the genus and is widely cultivated.