Orchids: indoor cultivation

Many orchids are relatively easy to grow, and given the right care will give a long-lasting flower display.

Cymbidium orchid. Image: RHS Advisory

Quick facts

Common name Orchids
Group Houseplants or greenhouse plants
Flowering time Depending on the species, all year round
Planting time Re-potting is usually best carried out in spring
Height and spread 10cm (4in)-1m (3ft) height and spread
Aspect Filtered bright light to partial shade
Hardiness Tender
Difficulty Moderate to difficult

Cultivation notes

Indoor orchids are mainly epiphytic (growing on trees) or lithophytic (growing on rocks). In their natural habitat this means using trees or rocks as a support and feeding from plant debris accumulated around their roots. There are some terrestrial species that grow in the ground.

Many epiphytic and lithophytic orchids can be grown in containers filled with open, free draining specialist orchid compost. They often form aerial roots outside of the container.

Re-pot only when the roots have filled the pot, using a container that is only one or two sizes larger. Do not try to bury the aerial roots in the compost, as they may rot.

Temperature and light

Orchids like a variety of temperatures, so choose the best position in the house to suit the needs of the particular orchid you are growing.

Cool-growing orchids such as Brassia, Cymbidium, Dendrobium, Lusidia discolor and Oncidium (cool) need a minimum winter night temperature of 10°C (50°F). A porch, heated conservatory or unheated indoor room would be ideal. If grown in warmer environment, their flowering is often reduced. They can be placed outdoors in summer in a shady position.

Intermediate temperature orchids such as Cattleya, Oncidium (warm), Miltoniopsis and Paphiopedilum prefer a minimum temperature of 13-15°C (55-60°F).

Warm-growing orchids such as the ever popular Phalaenopsis enjoy rooms indoor conditions all year round, with a minimum temperature requirement of 18°C (65°F).

Orchids generally prefer bright but filtered light. They need protection from direct sunshine.

Watering, humidity and feeding

Orchids prefer high air humidity, but their roots will rot easily in wet compost. Water them about once a week, ideally using tepid rainwater. Water from above and tip out any water that collects in the saucer under the pot. Alternatively, plunge the container into a bucket of water and allow to drain thoroughly.

Mist the foliage and aerial roots daily, or stand the pot on a wide saucer filled with gravel, filling the saucer with water to just below the surface of the gravel.

Reduce humidity in winter if temperatures are lower (this applies to orchids grown in porches or conservatories rather than those grown indoors, where temperatures are constant or may even rise in winter with central heating).

Orchids have different feeding requirements (see Growing specific indoor orchids section) but are not generally heavy feeders. As a general rule feed with a liquid orchid fertiliser every third watering during the growing season.

Many orchids need a rest period, usually during the winter months, when watering and feeding should be reduced.

Repotting

Repot every two years regardless of whether the orchid has outgrown its pot, as older orchid compost breaks down, preventing air reaching the roots which leads to disease. Always use proprietary bark-based orchid compost, never a loam-based or standard multipurpose one as these will kill your orchid.

When repotting monopodial (non-clump forming) orchids such as phalaenopsis, if the remaining roots comfortably fit the old pot after removing the old compost and any dead roots, then it is best to reuse it. Too large a pot means the compost will dry out too slowly after watering, resulting in root rot. Do not try to bury the aerial roots in the compost, as they may rot. Phalaenopsis can be repotted at any time of year.

With sympodial (clump forming) orchids such as cymbidiums which produce pseudobulbs (bulb-like stems attached to a short rhizome), use a pot that is just wide enough to allow for two years’ new growth. Cymbidiums are best repotted in spring just after flowering.

Growing specific indoor orchids

See our specific profile pages for how to grow the following orchids:
Cymbidium orchids
Oncidium orchids (cool section)
Oncidium orchids (warm section)
Paphiopedilum (slipper orchid)
Phalaenopsis (moth orchid)

Cattleya

Cattleya are prized for their brightly-coloured, showy blooms that reach up to 20cm (8in) across, produced in either autumn or spring.

Temperature

Daytime temperatures should be around 18-20°C (64-68°F), with nighttime temperatures not dropping below 13°C (55°F).

Light

Cattleya prefer bright conditions, but do not place in direct sunshine as this can burn the leaves.

Watering and feeding

In summer, allow the plant to dry out in between thorough waterings and apply an orchid liquid feed every third watering. Water more sparingly in winter and, for a short time, stop watering to ensure plants get a winter rest.

Potting requirements

Use a coarse, bark-based compost, such as a mix of 3 parts medium-grade bark chippings, 1 part perlite and 1 part fine charcoal. Repot in spring and then leave for at least three years.

Dendrobium

Dendrobium flowers can be single or in racemes. The larger dendrobiums produce flower spikes 90-120cm (3-4ft) high and therefore require support, but many varieties are half that height. They are one of the few orchids that produce flower spikes from the old pseudobulbs.

Dendrobiums fall mainly into two groups: those that need a lot of heat to grow well, such as D. bigibbum, and those that thrive in cooler conditions, such as D. nobile and D. speciosum. Dendrobuim cunninghamii from New Zealand is the hardiest species, thriving under glass in barely frost-free, airy conditions.

Temperature

Cool-growing dendrobiums flower best where the minimum night temperature is 10-13°C (50-55°F) during the winter months.

Warm-growing dendrobiums require minimum temperatures of 21-24°C (70-75°F).

Light

Partial shade is best in summer, but full light is needed from autumn to early spring. The canes of cooler-growing species will fail to ripen adequately unless given maximum light in winter.

Watering and feeding

From late spring to summer, grow in a humid, partially-shaded position, watering as soon as the compost dries, and mist daily when the weather is hot and sunny. Add an orchid fertiliser every third watering.

Keep plants drier in winter. The warm-growing species will grow throughout the year and need regular watering during the winter, but do not allow them to become waterlogged.

Hanging the pots can help to increase drainage and light, as well as helping avoid problems of top-heaviness when in flower, but avoid moving the plant once the flower spike is growing.

Repotting

Dendrobiums can be grown epiphytically on a bark slab in very humid conditions, or in epiphytic orchid compost in a container or slatted basket.

They resent disturbance and flower best in small containers, preferring to be pot-bound. However, once the plant fills and overflows the container (which may take three to four years), they can be repotted or divided in spring.

Ludisia discolor  (Jewel orchid)

This unusual-looking orchid produces spikes of white flowers in spring or summer that reach 15cm (6in) tall, and has striking leaves.

Temperature

Requires a minimum temperature of 10°C (50°F) and, ideally, 15°C (60°F) in the daytime.

Light

Lusidia grows in shade, so position on an east- or west-facing windowsill during winter, and move a little further back from windows during the brighter, summer months.

Watering and feeding

Water freely, allowing the compost to dry slightly between waterings. Mist during hot weather, or place pot on a tray of gravel filled with water to improve the humidity. Add a proprietary orchid fertiliser at every third watering. Keep plants drier in winter.

Repotting

Ludisia are terrestrial orchids that need a well-aerated, free-draining compost such as: 3 parts fibrous peat, 3 parts coarse grit, 1 part perlite and 1 part fine charcoal. Repot after flowering, half-burying the rhizomes in the compost, with the shoots uppermost.

Miltoniopsis  (Pansy orchid)

These orchids flower between April and September, and often twice a year. The blooms last four to six weeks and are often fragrant.

Temperature

A minimum winter temperature of 12°C (54°F) is needed, but it is acceptable for the temperature to rise to 25°C (77°F), especially in summer.

Light & position

Choose a shady position out of direct sun and away from draughts. If there is too much sunshine the leaves will become even paler and yellow. Move away from windows during winter.

Watering and feeding

From late spring to summer, grow in a humid, partially-shaded position, watering as soon as the compost dries and misting daily when the weather is hot and sunny. Add a proprietary orchid fertiliser at every third watering. Keep plants drier in winter.

Repotting

Use a proprietary orchid compost, and repot in mid-summer.

Pruning and training

Pruning of most orchids consists only of removing the spent flowering stems. See our individual profiles on different orchids for information on how to do this.

Stems carrying flowers are often weak and require staking to keep them upright.

Propagation

Propagation from seed requires specialist laboratory equipment, but some orchids can be successfully propagated at home by other means:

From plantlets: These appear from the growing points of stems of some Dendrobium, Epidendrum and Phalaenopsis species. Detach the plantlets when they have developed several good roots, and pot them up in orchid compost. Water them sparingly at first, and mist daily.

From stem cuttings: These can be taken from many Dendrobium orchids. Cut off a stem up to 30cm (1ft) long and cut it up into 7-10cm (3-4in) sections, with at least one dormant bud on each section. Place the cuttings in a tray of damp sphagnum moss, and keep them humid and shaded. Detach and pot up the plantlets that form from the buds.

By division: This method can be used to propagate orchids such as Cattleya, Cymbidium and Oncidium in spring, just after flowering. Only divide plants that are overcrowded in the pot. Cut through the rhizomes that join the pseudobulbs, making sure that each division has at least three healthy pseudobulbs. Trim off any dead roots and remove any brown and shrivelled pseudobulbs before re-potting the divisions individually.

Cultivar Selection

Orchids are often sold as unnamed hybrids and cultivars. To obtain named cultivars and hybrids contact specialist nurseries such as members of the British Orchid Growers Association.

Links

AGM Orchids

Problems

Common cultivation problems include:

  • Overwatering: Roots become soft and soggy. Root death causes collapse of the plant
  • Overfeeding: This causes root damage. In severe cases roots and compost are covered with fertiliser crystals. Plunge the pot in water to dissolve the excess fertiliser. Do not exceed recommended application rates and do not feed during the resting period
  • Sun scorch: This results in bleached, scorched leaves. Provide shade from direct sunshine
  • Failure to flower: May suggest the need for a rest period, and/or a lower temperature period to initiate flowering

Orchids can suffer from aphid, scale insectwhitefly, red spider mite and mealybug attack. If kept outdoors during the summer, protect them from slug and snail damage.

Orchids can be affected by various viruses. The symptoms include pale green to yellow spots, streaks or patterns of brown, black rings and other patterns of discolouration. There is no cure and affected plants should be destroyed.

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