RHS Journals

The Garden
February 2003

Orchids at home

Once the exclusive preserve of the aristocratic hothouse, orchids are now relatively inexpensive and widely available. A range of modern hybrids will grow successfully and flower in the home, as Isobyl la Croix explains

Images: Tim Sandall

Thanks to the plant-breeding technique of tissue culture, such beautiful hybrids as this X Odontioda Joe’s Drum selection are available for beginner orchid growers to cultivate in the home

Why do orchids still retain an air of mystery for many, regarded as plants that only experts can grow? Orchids recently became the most popular pot plant in Europe. And in garden centres and supermarkets throughout the country, flowering orchids can be found on sale for under £10. Some are named, often inaccurately, others are just labelled ‘orchid’. Unfortunately, many are in unsuitable composts and containers, with instructions that are, at best, vague.

Many who buy such plants will never have grown an orchid before and may treat their plant like a poinsettia, throwing it out when it has finished blooming. However, orchids can make excellent house plants and flower repeatedly given the right care.

The orchid industry

Orchids have become so widely available and affordable because of the revolutionary plant-breeding technique of tissue culture. Particularly fine cultivars can be selected and large numbers of genetically identical offspring can be grown, each from only a few cells. Raised under ideal, sterile conditions, these clones reach flowering size far more quickly than variable, seed-raised plants.

Orchids are grown on an industrial scale, and millions are raised in the Netherlands each year. Most are hybrids belonging to the tropical and subtropical genera Cymbidium, Phalaenopsis, Dendrobium, Miltoniopsis, Odontoglossum and Oncidium, and intergeneric hybrids derived mainly from the last two.

Home orchid cultivation

Like other house plants, orchids need light, but not direct sun (east- and west-facing windows are best, south-facing in winter only); they require warmth; they dislike draughts; and they need water.

Orchids differ from other house plants in their root systems, for most tropical species are epiphytes - they grow on other plants (usually trees), not in soil. Their thick and fleshy roots quickly rot if drainage is poor, so they should be grown in open, free-draining composts. To mimic the substrates in which the plants grow in the wild, orchid composts are usually based on relatively large pieces of bark with added perlite and charcoal. A modern inert alternative used increasingly by growers is rockwool, available from some garden centres, which does not break down.

Watering orchids correctly and a humid microclimate are the keys to successful indoor cultivation. More orchids die from too much water than too little, so always allow the compost to become almost dry before watering thoroughly again. Never allow an orchid to sit in water. The easiest place to water one is at a sink, as much of the water will pour straight through the open compost.

High humidity is another requisite, as orchids dislike dry atmospheres produced by central heating, and should not be placed in draughts or close to radiators and other heat sources such as on top of televisions. Stand pots on a layer of damp clay pellets or pebbles in a larger container or on a tray. It also helps if pots can be grouped together. Orchids usually tend to enjoy the humid conditions found in bathrooms and kitchens, and also benefit from a regular misting with a fine spray of water, avoiding any flowers.

Orchids are adapted to making do with little in the way of minerals. Fertiliser applied at full strength can damage the roots, so apply at a half to one-third of the usual rate, or use a specially-formulated orchid fertiliser.

Many orchids have swollen structures at their bases called pseudobulbs (as they are actually enlarged stems, not true bulbs) each bearing from one to many leaves that may last several years but are eventually shed. Even leafless pseudobulbs seem to be useful to the plants, and are probably used to store supplies of food or water.

Pests and diseases

Indoors, aphids are the most likely pests; they gravitate to flower buds and new growth but are easily wiped off. Scale insects look like small, brown limpets or flat, white insects and they, too, can be wiped off or sprayed with Provado Ultimate Bug Killer aerosol.

Mealybug is often a problem on orchids and can be difficult to control. In the home, as for scale, treat by wiping off or using the Provado spray (above).

Red spider mite can be a serious pest in a glasshouse - because they are so small, the grower is usually aware of them only after damage has been done and the leaves develop a yellow mottling and fine webbing. Under glass, and in the home, biological control with a predatory mite (Phytoseiulus persimilis) is an option (there is no risk of it becoming a nuisance indoors), or plants can be sprayed with a proprietary insecticide that the label says is effective against spider mite. Keeping plants well misted also discourages this pest.

Bacterial rots and fungal spotting on leaves are almost always the result of poor cultural practices, such as overwatering or allowing water to lodge in growing points. Prevention is easier than cure; once rot has started, it is often too late to save the plant, but if just a small area is affected, cut it away and dust with sulphur powder.

Any reputation orchids retain for being ‘difficult’ is increasingly undeserved, provided their particular needs are understood and met. The sense of achievement in seeing the first flower of a new spike open on a plant you have coaxed back into bloom yourself is enormous. There is a world of beautiful orchids out there - do come and join it.

Orchid Dos and Don'ts

Don’t let orchid pots stand in water, or water too frequently
Don’t allow water to lodge in leaf axils or growing points
Don’t put orchids on windowsills in full sun
Don’t stand them close to heat sources such as above radiators or on top of TV sets
Don’t put them in a draught
Don’t put plants near a bowl of fruit - ripening fruit gives off ethylene gas which makes flowers go over quickly.
Do join an orchid society - most people have one within reach. Beginners are always welcome and it is an excellent way to learn about orchids and acquire plants. Details of local orchid societies from: The Secretary of the British Orchid Council, Mr E S Manning, Estover, 25A Forest Road, Tarporley, Cheshire CW6 0HV, or e-mail him
Do read about orchids. Many books are available, often aimed at beginners. The RHS orchid journal, The Orchid Review, is published every other month and contains articles on all aspects of orchid-growing, catering for all degrees of expertise. A year’s subscription is £25 in the UK. Write to The Orchid Review, RHS Subscriptions, PO Box 38, Ashford, Kent TN25 6PR. Tel: (01303) 813803; mailto:orchidreview@rhs.org.uk
Do go to orchid shows. Most societies have a show once or twice a year, usually with trade stands selling plants and sundries.

Repotting and division

	When the compost has begun to break down into smaller pieces and lose its open structure, or if new growth is pressed hard against the side of the pot like this cymbidium, it is time to repot, ideally in spring. Some growers repot annually but be guided by the structure of the compost. Most garden centres sell orchid compost, but it can also be worth contacting specialist orchid nurseries or societies
	Turn the plant out of its pot; if the roots are sticking to the side and making this difficult, soak it in a bucket of water for about half an hour. Shake off all the old compost and trim off any dead roots (living roots are firm and whitish, dead roots are brown and soft). Cut away any shrivelled, dead pseudobulbs at the same time. Use clean tools and disinfect them between different plants to avoid spreading diseases. Only divide the plant if it is unmanageably large, or it naturally separates into pieces
	Use the smallest pot that will accommodate the plant’s roots and put a layer of drainage material such as polystyrene chips in the bottom. Holding the plant upright, feed fresh compost (here based on rockwool) around the roots, taking care not to damage them by firming the compost.
	Water newly-repotted plants sparingly until their roots have recovered from the disturbance

European Orchid Conference and Show 2003

Together with the British Orchid Council, the Society is organising the European Orchid Conference and Show 2003 (13 - 16 March) in the RHS Lindley and Lawrence Halls, London. Visit the show website

Click here to find out more about specific orchids that are best suited for the home

Isobyl la Croix is Editor of The Orchid Review

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