IN THE GARDEN
Care and cultivation The Cambridge University Botanic Garden has few native terrestrial orchids, although bee orchids do appear spontaneously and we have an established population of the common spotted orchid ( Dactylorhiza fuchsii ). Our glasshouses, however, provide a range of environments in which we grow several hundred species and cultivars from a diversity of habitats and climates across the globe. In cultivation, tender orchids resent standing in water and need free-draining, composted bark. They should only be watered as the compost dries, so weekly is usually sufficient in summer. Epiphytic species will also grow well when mounted onto bark and frequently sprayed with water to maintain a humid atmosphere. Some genera are familiar, such as the Phalaenopsis (moth orchids) and Cymbidium cultivars, which are readily available and easily grown at home, even by those who consider themselves horticulturally challenged. Both of these species require little input, provided they are given the correct conditions. Moth orchids thrive in bright light, ie a south- facing windowsill, at temperatures above 16°C; while Cymbidiums prefer slightly cooler temperatures (but at least 10°C) and good light (but not direct sunlight), ie a west- or north-facing window. Other genera are more demanding and challenging in cultivation, and some
FLOWER POWER Vanilla planifolia (top left), the Angraecum sesquipedale (middle) and the Bulbophyllum phalaenopsis (bottom)
species that we grow here in the Garden are rare in cultivation and in the wild. Prize specimens Several species are of particular note in our collection. Vanilla planifolia (vanilla) is a trailing orchid growing up to 15m in length and bearing fleshy aerial roots that help it
cling to host trees. A native of Mexico and north and central South America, it grows in lowland tropical forests, but is now rare in its native range due to habitat destruction and over-exploitation. Today, vanilla is grown more extensively in South America, Java, New Guinea, Malaysia, the Seychelles and Madagascar, although the absence of its natural pollinator (the Melipona bee) means that this species must be pollinated by hand in order to produce vanilla pods. Angraecum sesquipedale (Darwin’s orchid) is a tropical epiphytic species from Madagascar. A winter-flowering species, it has a waxy-looking white flower with a nectar spur (an elongated part of the flower containing the sugary liquid) of up to 45cm. Darwin predicted that this flower could only be pollinated by one specific insect with a proboscis (tongue) long enough to reach the nectar at the base of the spur. He was correct in his prediction, but it was only after his death that one species of hawk moth, with a suitably
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