Growing Orchids in the Greenhouse

Orchids are, all too often, looked on as specialised plants which need a green-house to themselves. This is not the case. Certain orchids can be grown in the average-sized amateur’s greenhouse together with other plants. Cymbidiums are possibly the easiest of all, with paphiopedilums the next easiest. Others which can be grown are Coelogyne cristata, dendrobiums, Cattleyas and odontoglossums.

Ordinary compost is not suitable for orchids and the special requirements of each genus is detailed in the notes which follow. Osmunda fibre is expensive for it is imported from Japan, but bracken fibre has been used successfully on many occasions as a substitute. Other ingredients of orchid composts are turf fibre from which the loose soil has been shaken away, flaky decayed oak or beech leaves, farmyard manure at least 12 months old and broken up into pieces the size of walnuts, peat fibre and sphagnum moss. All orchids must have good drainage with broken crocks in the base of the pots supplementing the free-draining compost mixture.

Cymbidiums

The many cymbidium hybrids available have an enormous colour range. They flower from January to May or June, depending on the temperature and conditions under which the plants are grown. A minimum temperature of 10°C. (50°F.) is desirable but it can go down to 7°C. (45°F.) if necessary.

Cymbidiums are best grown in light. Fibrous loam with a little sphagnum moss and peat fibre added. When potting, allow the thick fleshy roots plenty of room and make sure that the drainage is good. Repotting is necessary every second year and is done when flowering has finished. While they are in active growth from May to August or early September, cymbidiums need plenty of water and a feed with liquid or soluble fertiliser about once a fortnight (it must be given at much lower strength than for other plants – about 50 per cent.). Shade from strong sunshine is needed in summer. Water supplies should be reduced in winter without allowing the plants to dry out.

Cymbidiums are increased by division or by repotting the pseudo-bulbs in March. Plants should, however, be left undisturbed for as long as possible as they take a long time to develop flowering stems.

Paphiopedilums

The Lady’s Slipper Orchids are still familiar to many people by their old name. Cypripedium. They are extremely handsome plants with beautiful flowers – excellent for cutting – and, usually, large. Leathery, mottled leaves. The two most frequently grown are Paphiopedilums insigne, with purple-spotted greenish-yellow flowers, and its yellow and white variety sanderae. They flower in winter and spring.

These plants should be grown in a mixture of equal parts peat and fibrous loam with sphagnum moss and broken brick added. Drainage must be excellent. Potting is done in spring, after flowering.

They need plentiful supplies of water at all times but rather less in winter than during the rest of the year. Shade is needed from strong sunshine in summer. And a temperature of 13 to 18°C. (55 to 65°F.) in winter. Increase is by division of the plants in spring.

Coelogyne

Coelogyne cristata

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Another interesting orchid is Coelogyne cristata with white blooms attractively marked with yellow in the centre. It flowers in the spring, and sometimes into early summer and is a good plant for a hanging basket in a greenhouse, sun lounge or conservatory. It needs very similar treatment to cymbidiums. Increase is by division.

Dendrobiums

This is a huge genus which includes something like a thousand species, both ever-green and deciduous, and countless hybrids needing varying cultural conditions. A popular range for the amateur gardener are the hybrids of Dendrobium nobile in colours which range from purple and pink to yellow and white. These need a minimum temperature of 10°C. (50°F.) in winter when they are resting, rising to 16 to 29°C. (60 to 85°F.) in summer. The flowers are borne during late winter and early spring.

Pot in spring in a mixture of 3 parts osmunda fibre and 1 part sphagnum moss. The plants must be watered freely in summer, given light shade against strong sunshine, and kept in a moist atmosphere. The water supply must be much reduced in winter, at the same time not allowing the pseudo-bulbs and leaves to shrivel. Increase is by division.

CATTLEYAS

The very handsome, epiphytic, large-flowered cattleyas are plants for the warm greenhouse needing a minimum temperature of 13°C (55°F.) in winter, then increasing to 18 to 21°C. (65 to 70°F.) in summer. Mauve, purple, white and yellow are colours found in cattleyas, and flowers appear in summer and autumn.

Potting is done in spring or early summer using a mixture of 3 parts chopped sphagnum moss and 2 parts osmunda fibre, with a sprinkling of broken charcoal added. Shade is needed against strong sunshine in summer and a moist atmosphere must be maintained. Water freely in summer, but much less so for a month or two after flowering and in the spring. Increase is by division of the pseudo-bulbs when repotting.

ODONTOGLOSSUMS

Odontoglossum crispum

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These are orchids for the moderately heated greenhouse needing a temperature of 16°C. (60°F.) in summer and winter. There are many lovely hybrids of Odontoglossum crispum with long, arching sprays of flat flowers produced most of the year. The white petals are marked with such colours as yellow, pink and purple.

Pot odontoglossums in March in a mixture of equal parts chopped sphagnum moss and osmunda fibre. Water should be given sparingly at first but in greater quantities later as growth develops. Fairly heavy shade is needed from May to September and keep the atmosphere moist at this time by syringing. While the plants are resting in winter they should be kept only just moist. Increase is by division.

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01. March 2012 by admin
Categories: Greenhouse Cultivation, Greenhouse Management | Tags: , , , , | Comments Off on Growing Orchids in the Greenhouse

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