Sandy’s Garden ... Dendrobium orchids

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It is said that confession is good for the soul.

And if this saying is correct, then I am about to do my immortal soul a good turn, for I am going to make not one, but two confessions. I do not really enjoy Islay whisky. That’s the first. Yes, I am very well aware that the true whisky connoisseur waxes lyrical about the peaty aroma and taste … but it’s not to my taste. And the second confession is that I don’t really like orchids. That’s not to say that I don’t quite often have at least one orchid in the house, for orchids are well-regarded as gifts, especially for people who have a reputation for liking plants. But I don’t go overboard with enthusiasm for these popular epiphytes; and, very possibly because I am not over-enthusiastic about them, I have never really learned how to care for them properly, and they reward my ignorance by not doing too well in my home.

However, there are distinct advantages to playing host to dendrobium orchids, advantages that we shall come to later. First of all, let’s establish what they are and how to look after them properly. Most orchids are epiphytes, meaning that they are parasitic plants which grow on other plants, most often found clinging to the bark of trees. They are very good hangers-on and it is not easy to prise an orchid free of its chosen host in the wild. And it is this characteristic that is responsible for their scientific name Dendrobium, which comes form two Greek words – dendron and bios, meaning ‘a tree’ and ‘life’. Strictly, Dendrobium plants are members of the orchid family and it’s a bit of unnecessary repetition to refer to them as dendrobium orchids: but it’s usually done this way. They are commonly known as ‘greenhouse orchids’ but are probably more often found as house plants nowadays; and they are widely available in the house plant sections of garden centres.

Like any houseplant, it is an excellent idea to keep the instructions for their care handy if, like me, the memory isn’t quite as good as it once was. In general terms, dendrobium orchids are best grown in a commercially-prepared orchid mix or in decayed oak leaves, Spanish moss or sphagnum moss; and the prepared orchid mix is probably the easiest to find. During the daylight hours, they like a temperature of at least 16°C … say, 60°F … but of no more than 24°C or 75°F: but … and here’s the one rub … they really don’t like the temperature to fall below 13°C … say 55°F … during the night hours; and many people allow the temperature in even the warmest part of the house to dip below that during cold winter nights. Still, provided the plants are never left trapped behind the curtains on a winter’s evening and are kept well away from any draughts, they’ll have a pretty good chance of surviving in a warm living room

And now for the benefits. Well, apart from the attractive flowers, dendrobium orchids are long-lived (allegedly!), which reminds me of a splendid American definition I came across: ‘a perennial plant is one which would have lived for several years had it survived’. These orchids are very good at removing chemical vapours from the air … and yes, almost everyone has sources of chemical vapours in their living rooms, from the carpets and the upholstery to the cleaning agents and polishes, the chemicals including things like alcohol, acetone and formaldehyde They are also good at resisting the infections that plague many house-plants provided the atmosphere is not too dry and they are not given too much water. Dendrobium orchids have one habit which is of no real concern to householders but is, nonetheless, rather unusual; they take in carbon dioxide and release oxygen during the night, the reverse of the time when most plants do it. But remember … keep the care instructions!

Sandy Simpson, Polmont Horticultural Society