Hoya carnosa: Wax Flower, Porcelain Flower
The wax flower is one of the commonest climbers grown for room decoration, be it the typical green-leaved form or the variegated cultivar ‘Variegata’. It is a member of a genus embracing some 100 species, found over an area extending from southern and south-east Asia through Malaysia and the Philippine region to Australia.
Hoya carnosa (syn. Asclepias carnosa) is native to China and Queensland. The beautiful(particularly lovely when viewed close-up) are produced from May until late autumn. Plants grown indoors, flower much better in a soilless medium (hydroponics).
The small species, such as H. bella from Burma, are much in demand. This, however, is not a twining plant; it forms an upright, much-branched shrub with pendant twigs at the tips. The leaves are barely 2.5 cm (1 in) long. The flowers are quite large in relation to the size of the plant for they measure up to 1.5 cm (over lk in) across; they are likewise borne in clusters at the tips of the branches.
Some species have proved to be very good in terrariums where the firm leathery leaves are not damaged by small animals. These include first and foremost the narrow-leaved H. longifolia from the Himalayan foothills, a small twining plant with attractive flowers, which, as in the species, are produced more readily in soilless cultivation.
H. imperialis from Malakka is a beautiful but rare species with leaves up to 20 cm (8 in) long and drooping clusters of flowers up to 7 cm (2-3/4 in) across and coloured dark purple with a white centre. Quite common, on the other hand, is Hoya (syn. Centradenia) multiflora with beatiful clusters of yellow flowers resembling those of the wild rose.
Although many wax flowers have been grown in cultivation for a long time, centrally-heated homes now make it possible to grow the more tender species. The compost should be a mixture of peat and sand with a little leaf mould added or one of the peat-based potting composts and in summer the plants should be watered liberally. Propagation is easy; simply insert a cutting with one pair of leaves or just a leaf by itself into an ordinary rooting medium in a warm propagator where it will form roots in a few weeks.