Calanthe is a genus of about 150 terrestrial species spread through parts of Asia. Of these, only a handful of species and hybrids are in general cultivation. The genus can be divided into two distinct groups. The first, which is more widely grown, contains deciduous plants that have large, silvery pseudobulbs and wide, spreading, ribbed leaves.
The plants were at one time included in the genus Oncidium, but are now considered distinct, although the latter name persists in orchid-growing circles. Very few of the species, and virtually no hybrids, are cultivated.
Mostly the species are rare and much treasured. The main appreciable difference between Cyrtochilum and Oncidium is the size of the lip, which, so often exaggerated in the oncidiums, is much reduced in favour of broad, spreading sepals in the cyrtochilums. The plants, which can be over 30cm (12in) tall, produce robust pseudobulbs with narrowly oval leaves.
Calanthes have a short, fast-growing season. Because of the speed at which they grow, these are really exciting orchids to cultivate, but they do need plenty of headroom while in leaf. Repot each spring when the growth starts. If the oldest pseudobulb is dead and shrivelled, remove it; if it is still firm and plump, it may be potted separately to give you two new plants next season.
Temperature is intermediate-growing, with a minimum temperature of 16C (60F) at night. Grow in pots of a terrestrial orchid mix containing some peat and perlite. Begin watering and feeding as soon as new growth is seen in the spring. While in growth, the plants should be kept well shaded. Too much humidity, as well as spraying of the leaves, can cause the foliage to spot. This is not a great problem because it is shed in autumn, after turning yellow.
In winter and spring, little flowers less than 1cm wide adorn the pretty Cirrhopetalum gut tulatum, which can be easily grown and does well indoors or in a cool greenhouse. The flower spikes are under 15cm (6 in) tall. Cirrhopetalum umbellatum A robust species with plants over 15cm tall, this has drooping flower spikes that terminate in umbels of large flowers where the sepals are extended to form the edge of the ring. The petals and lip are very small. The flowers bloom in spring.
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