Dipladenia x sanderi ‘Rosea’
Anyone who comes across one of the botanical species of this genus growing in the wild (there are 40 of them distributed in tropical America) will find it hard to believe that it is not a cultivated plant when he sees its magnificent large.
Dipladenias are not newcomers to cultivation but they were relegated to the ranks of forgotten plants until 1955 when they were ‘rediscovered’ by Danish nurserymen and introduced to the market. They evoke such great interest that nowadays this climber appears on the list of many horticultural establishments.
Pure species are not found in cultivation, however, only hybrids derived chiefly from the crossing of several Brazilian species, primarily D. sanderi, D. atropurpurea, D. eximia and D. splenderis. They are robust, woody climbers with firm, glossy, dark green leaves and large, funnel-shaped flowers joined to form a tube at the base. The fruit is a large, heavy, double follicle that exudes a thick poisonous milk when bruised and later dries up. The seeds are small, flat, dark brown and furnished with long hairs that aid in their dispersal by wind.
Dipladenia is a rewarding house plant that flowers regularly and profusely. Its requirements and cultivation are much the same as those of allamanda. The substrate, however, should be lighter and more porous, for the roots do not tolerate lengthy contact with water. John Innes potting compost No. 2 with extra peat added would be suitable.
Propagation is also the same as for allamanda. When the plants are hard pruned in spring use the prunings as cuttings. These should be rinsed in warm water (to release the milk) and inserted in a mixture of peat and sand in a warm propagator. They root more easily than allamanda – within 3 to 4 weeks.