Getting orchids to bloom is one of the most common of gardening conundrums

ONE OF THE questions that this column is regularly asked is: "Why won't my orchid flower again?" And, while I do my best to answer, I have to admit that orchids are a bit of a mystery to me. They are like a confederate nation of plants – they don't obey the same rules as other green things. "Even the most advanced of gardeners throw up their hands," says orchid expert judywhite (whose elided, lowercase name dates from the 1980s when she was a humour writer for publications such as McCall'sand Seventeenin the US). To help those of us who are mystified by this seductive group of plants, she has written a guide, Bloom-Again Orchids, published by the excellent horticultural specialists, Timber Press.

“The real trick,” she says, “is to understand that they would much rather be hanging from the side of a tree than living in a pot.”

And indeed they would, because the tropical and subtropical forebears of our domesticated orchids are epiphytic, that is, they grow on trees or shrubs. Their diet is lean: they get nutrients from the moist rainforest air, from rain and from the particles of decaying matter that fall around the plant. “Normally it rains very, very hard, and then the water runs off and the plants dry out.”

Orchid compost is therefore fast-draining, and usually consists of a mixture of bark pieces and various additives (which may include charcoal, perlite and moss).

Overwatering, says judywhite, is the “number one” reason many orchids waste away, or fail to flower again. Overfeeding is another cause, while the wrong light level may also prevent reblooming. “Look at the leaves; if they look dark and lush the plant is not getting enough light. You want them to look grassy green.”

Orchids are unhappy in a dim north-facing window, and if you can provide only an east-facing aspect, the plant needs to be as near to the window as possible. South- and west-facing windows offer the most potential, although if the light or heat is too extreme, the author recommends veiling the glass with a light curtain, or moving the orchid back a little.

Different orchids, however, have different light and heat requirements; they will sit around doing nothing much if the environment is unsuitable. "Make sure you pick the right orchid for your conditions," says judywhite, who details the specific requirements of 50 of the most commonly available orchids in her book. If you live in a centrally-heated house or apartment and don't have high light levels, she suggests growing Phalaenopsis(known also as the moth orchid). Alternatively, if you live in a cooler, but brighter house, try Cymbidium, the first orchid to be cultivated – a favourite of Confucius, apparently.

I'm delighted to take this advice from judywhite, who has some serious orchid credentials to her name; she wrote and photographed Taylor's Guide to Orchidsin 1996, she has travelled the world looking at orchids in the wild, and she was awarded the American Orchid Society Silver Medal for outstanding service to the orchid community. At one time, she owned around 1,000 orchids. At present, however, because she divides her time between Pennsylvania and Northamptonshire, she has culled their number to a mere 25 or so. As she says herself, "I have killed orchids on both sides of the Atlantic." Spoken like a true gardener.

Bloom-Again Orchids by judywhite (Timber Press, £9.99). Available at good bookshops, or online at bloom-again-orchids.com

ORCHIDS RISING

IN TIMES PAST, orchids were the preserve of a few, specialist growers. They were difficult to propagate, so plants were rare, and prices high. Collectors usually had deep pockets, and often had specially built conservatories in which to house their treasures. But modern science has changed all that. Humans learned how to grow orchids from seed, and they are now germinated in their thousands in sterile conditions in laboratories. We also learned how to clone the plants from minute pieces of tissue, making it possible to reproduce millions of identical replicas from a single plant. This is why the world’s most popular orchid, Phalaenopsis, is now available in garden centres, supermarkets and DIY shops for just a few euro. Other developments in orchid breeding have produced intergeneric crosses, where species from different genera are bred together to produce man-made hybrids. These are more vigorous and resilient, and have more showy flowers than natures creations.

GETTING IT RIGHT

• Choose the right variety for your conditions: match its requirements to your light levels and your temperature range.
• Don't overwater, or let the pot stand in water.
• When you do water, do it correctly: bring the plant to the sink, and thoroughly drench the compost under the tap. Let the water drain completely before returning the pot to its saucer.
• Feed your orchids "weekly weakly". Use orchid feed, which is specially formulated for the species' lighter diet.
• When you re-pot, use orchid compost, which is suitably free-draining.

DATE FOR YOUR DIARY

April 24th, 1.30-4pm: Alpine Garden Society Silver Jubilee Show at Cabinteely Community School, Johnstown Road, Dublin 18. Spectacular show of expertly-grown alpine plants. Plant stall and nurseries. Teas. Raffle. Admission: €3