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Coelogyne Cool Growing Coelogynes By Peter White

The first thing is to impress all that by cool we meant 55 degrees Fahrenheit (12 degrees Centigrade). Although there are Coelogynes which prefer warmer conditions, in this instance we will concentrated on the cool growers, most of which have fragrant white flowers with some yellow or orange on the lip.

There are over 100 species of Coelogynes; the warmer-growing ones are fussy plants and are difficult for the amateur to grow successfully.

The majority of Coelogynes are native to the Himalayas, Bhutan, China, Vietnam and the Philippines, with some reaching as far as Fiji. There are no books devoted to Coelogynes alone – yet – but Dudley Clayton, a leading UK expert, has one in the pipeline.

At the higher elevations these plants are subject to cold winters with some overnight snow, and bright cool summers. C. cristata, C. fimbriata and C. mooreana are the very cool growers. They require a winter night temperature down to 45F (7C) and never above 50F (10C), with a rise of about 15F (8C) during the daytime. In winter the plants need a rest while the new growths mature and form their flower buds, so from the end of October to the end of January they should be kept just moist, but never allowed to dry out completely. What they need is just enough moisture so that the pseudobulbs remain plump. If signs of shrivelling are seen, a spray of water over the whole plant and the top of the growing medium should be given. Smaller plants need to be kept moister in winter as, having smaller reserves, they will dehydrate more readily than the larger plants.

In summer they need copious amounts of water, I use ordinary tap water. Indeed, C. cristata can be stood in a shallow saucer of water to some advantage at this time of year.. As orchids go they are also quite greedy feeders. In May to August Peter uses a high Nitrogen feed at Cymbidium strength (700 to 1000 ppm), and in September and October he changes to a high Potash feed, the same as many people feed to their tomatoes, again at Cymbidium strength. With this regime Coelogynes will flower in the late winter, from January to March or April, and are often highly scented. The flowers are long lasting too, so they will make good houseplants for a cool room provided that the required cold winter rest can be provided.

Coelogynes that need it can be repotted immediately after flowering. It is usual to repot every second year; do not be tempted to divide the plants unless absolutely necessary as they may refuse to flower the next season. Only split the plant if the centre has deteriorated and needs to be discarded, or if the plant is so big as to be unwieldy. They do best if simply dropped into a larger pot and the space around the rootball filled in with new compost. This way a magnificent specimen plant can be obtained, if one has the room. As for the medium, I suggests fine to medium bark with a top dressing of sphagnum moss. Shallow baskets and half pots work very well, but not bark rafts as they are too dry.

Few insect pests seem to bother these species to any great extent. Scale is something to watch for and eradicate if it arises. Black tips to orchid leaves are often a sign of over-feeding, but in Coelogynes it seems to be a normal habit of the foliage of a mature specimen. Black or dark brown spots and streaks, particularly on the underside of the leaves, are also very common. While they may indicate viruses, these are rare in Coelogynes.

High light levels are needed all year round although foliage will burn in summer if it is ‘overcooked’. Because of this need for light they are often happy when hung near the roof of the greenhouse, as long as they are within reach of the watering can.

C. alata will grow well in the plastic mesh baskets that are generally sold for aquatic plants. It has many small creamy white flowers with bright orange on the lip and will last up to three months in flower.

C. cristata has glistening white twisted petals with a bright yellow centre to the lip, 7-8 flowers per bulb, 3” or more across and a scent of jasmine. To see Coelogyne cristata click here.

C. cristata var. lemoniana has a pale lemon yellow centre to the lip.

C. fimbriata is a small creeping plant. The flower is pale yellowish to light brown with a brown to blackish blotch on the centre of the lip and a faint musky scent.

C. flaccida has an orange lip that is darker than C. granulosa.

C. granulosa has an orange/yellow lip.

C. mooreana has up to eight glistening white flowers with orange on the lip.

C. ochracea has the best scent of all but it does not do well as a houseplant. It flowers on erect stems with 7-9 blooms that are white with an orange/yellow lip.

Not many Coelogynes are hybridised today, but they will form crosses with Zygopetalums and Pleiones. These hybrids, I suggests, might suit British growers very well.

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