Going back to their roots

Houseplants feel homesick, too.

Sitting on millions of windowsills are homesick creatures craving for love and attention. They are houseplants, and the reason why their leaves turn brown, flowers shrivel, and stems wither is because we don't understand their ecology. The key to growing many houseplants is to appreciate the life of their great grandparents in the wild, where they are often superbly adapted to tough environments.

Centrally heated homes are so dry that to most plants they feel like a desert. That's fine for cacti and succulents, but be warned that these plants are also used to strong sunlight, so in our insipid winter sunshine they go into a sort of plant version of hibernation during which they should be left unwatered.

But for houseplants from damp tropical rainforests, the dry indoor air is a big headache. Begonias, fittonias, marantas and calatheas are among plants adapted to humid air, and the African violet actually drinks moisture from the air through the fine hairs carpeting its leaves - in its native home in Tanzania it's fed by mists rolling off the Indian Ocean. There are ways of providing extra humidity: standing the pots on wet stone, putting saucers of water under the leaves, misting leaves, standing groups of plants together so they keep each other moist, or putting them in kitchens and bathrooms, which are usually the most humid rooms.

Forest floor plants are also superbly adapted to scavenging for light in a dark environment. Begonias even have miniature spectacles peppered across their leaves to help focus beams of light down inside, and the crimson undersides of their leaves act like the silver backing on mirrors, reflecting back any light into the leaf. So these plants appreciate being well away from sunny windowsills where they'll fry to death.

Sometimes you need to understand plant behaviour. If your Indian rubber plant sheds its leaves it's often because it hasn't been watered, so the plant thinks it's the start of a full-blown Indian drought and time to drop its leaves to seal up any water leaks. But after a good watering it seems like the monsoon season has arrived, so the plant puts on a big spurt of growth.

In fact, watering houseplants can be a minefield- too much and you can give your little darlings the plant equivalent of a heart attack; too little and they wilt. But one plant is impossible to overwater - the umbrella plant. A cousin of papyrus, used to growing in swamps and riverbanks, it is extremely happy standing in a jar of water with a bit of soil at the bottom.

If you've got a real knack for throttling houseplants, it's worth considering some reallytough characters. The Kentia palm comes from the Lord Howe Islands in the South Pacific, where it's battered by sally winds and shrouded in deep shade from neighbouring trees. This makes it a masochistic houseplant, tolerating draughts, lack of water, overwatering and near darkness. Other plants can put up with intense sun, heat and dryness and even the inferno of a nearby radiator: the succulent crown of thorns from the arid lands of Madagascar and mother-in-law's tongue from the dry east of South Africa, for example. And the weird air-plants from the treetops of Central America are so tough they can be left dangling in mid-air without soil and only a light misting every now and again.

Your home is full of interesting ecological niches. For instance, don't be afraid of using cold, draughty windowsills at this time of year because to a flowering bulb plant they feel like bliss - a reminder of the mountains of Turkey where most of them originally come from, and where they flower in the bitter cold of early spring. This is why cyclamens, hyacinths, miniature daffodils and snowdrops shrivel up in warm rooms: they think it's summer and time to die back into their bulbs or corms for the summer drought.

Sad to say, many of these plants might be thriving indoors, but out in the wild their relatives are suffering a wretched life. Many tons of wild flowering bulbs are being dug up in Turkey for the European horticulture trade, and it's worth asking whether the bulbs you buy are picked from the wild or artificially propagated. Other plants are suffering from greedy plant collectors and the loss of their homes - some of those big cacti and cycads you see in office atriums were originally stripped out illegally from Mexico and Africa. Maybe one of the cruelest ironies is that the African violet is now one of the world's most popular houseplants, but in Tanzania it's only got one toehold left in the forests of the Usambara hills.

This article is based on a six-part television series, 'Potted Histories', on BBC2, 9.50-10pm, starting 4 January, with an accompanying book (BBC, pounds 9.99).