Tuberous-rooted perennials, imported into Europe from Mexico as early as 1600. Botanists soon started to cross the existing species and an enormous variety of large-flowered garden forms has been developed. None of them are winter-hardy, and the tubers must therefore be lifted every winter to be kept in a frost-proof place.
are used on a large scale as summer-flowering garden plants, especially together with in beds. Not everyone appreciates the vivid colours, which make it difficult to combine dahlias with other – herbaceous perennials for instance. In that case it is best to confine dahlias to beds of flowers for , especially the tall-growing strains which must be sup-ported by stakes or by coarse netting spread over the bed when the plants are still small. There will be flowers for until well into autumn.
Dahlias require good garden soil, enriched with rotted stable manure, dried blood or, if necessary, with artificial fertiliser.
Propagation: and culture Dahlias may be grown from, but this method will produce an odd mixture, which may nevertheless include very fine specimens. Sow from early spring onwards in a temperature of 18°C. Prick out the and grow them in a cold frame until they are moved outside in late spring.
Division of the tubers orfrom is a more usual method. In early spring the tubers are laid in trays or boxes filled with peat fibre or light garden soil, kept at a temperature of 15°C. When the tubers start to put forth shoots they may be cut up in such a way that every section bears a shoot. The cut surfaces are left to dry out and dabbed with charcoal or with a fungicide. The sections are potted separately and are initially kept under glass. In order to take cuttings, the tubers are also allowed to start into growth at a reasonable temperature. Remember that the first few shoots will produce the worst plants; unless you wish to grow a large number of plants, these are therefore discarded. The next few shoots are allowed to grow to 5-7 cm and are then severed close to the tuber. The lower are removed and the cuttings are inserted in a mixture of sand and peat, under glass, in a temperature of 15-20°C. Make sure that the succulent do not rot and keep them in a frost-proof place.
Dahlias are very sensitive to frost and should preferably not be moved outside until late spring. If there should still