If your fern turns brown in spring because you have kindly fertilised it, only to find out that juvenile fern fronds are killed by normal strength plant food and it should have been diluted to about quarter strength, throw its corpse in the compost (remove the pot first) and head to the garden centre. After your once fabulous fern slowly declines in its corner of the bathroom for a year or so, till it is mostly stick with little greenery, say farewell.

Or, just possibly, in any of the above cases, stick your fern outside in a semi-shaded area, preferably by the garden tap where it may get accidentally watered, and it will probably recover. For some reason neglected ferns flourish, while cossetted ones only last a season or two. This is probably because your bathroom, family room or study is not a fern's natural habitat, unless your roof's blown off and silt has washed across the floor, in which case you might suddenly find you have a fern carpet.

Ferns like moist soil, humid air and plenty of dappled light. Your bathroom is probably perfect in terms of humidity, but unless you have large bathroom windows your ferns won't get enough light to thrive, or even survive, long term. Of course large bathroom windows also need tolerant neighbours. Wombats, for example, are totally uninterested in anything that happens though our bathroom windows, though our guests sometimes need to be convinced of this.

Ferns also like moist soil, but not wet soil, which may lead to rotting roots. Your fern is heading for disaster if it wilts. Once a frond wilts it does not unwilt. It is heading for disaster more slowly if it isn't putting out new fronds to replace the old ones that die off.

Maidenhair is even fussier about a moist-warm-but-not-hot-and-not-cold-but-just-right air than fishbone and sword ferns. I watched a friend successfully cosset her maidenhair ferns with a mist spray every couple of days for humidity, a little diluted seaweed fertilser every few months in summer. She even had a 'plant sitter' to water the garden, and her indoor plants, twice a week in the summer holidays. Sadly, the plant sitter forgot to mist the maidhair's leaves, and its owner came back to find damp soil but brown-leafed ferns.

The ferns of my childhood were what grew along the shady side of the kind of house that was not inhabited by an avid gardener. I don't think I ever saw an indoor fern until the 1970s, when suddenly potted ferns were dangling in every second café and you could hardly see your black forest cake or choc chip cheesecake for greenery.

Then in the late 80s I was suddenly confronted with a house full of them. The man I had just fallen in love with decided that the best way to impress a woman who owned 400 fruit trees was to fill his house with foliage. He called in to the garden centre on the way home from work and bought every potted fish fern they had. They stared at me as I came through the door: fish ferns in the hallway, on the fridge, on the dining room table, hanging in the bathroom, on each bedside table.

It took us a fortnight before we both realised that neither one of us knew how to care for a potted fish fern, and the poor things were fast turning brown.

So I watered them - I did know that much about ferns. And they didn't die, at least not for a year or two, just slowly dwindled till we had to admit they did not serve their allotted purpose i.e. to be decorative, and threw them out, under the fig tree in the back garden, the place where lawn clippings and prunings and other garden debris were hidden, and where the fish ferns decide to take root.

They are probably still happily growing there, free from human interference. And also, quite probably, if I had had the patience to let them rejuvenate, they might have returned to be gorgeous indoor greenery. A fern may look like a leafless lump, but it may still put our fronds after a few months of dampness and dappled light. And if there is just one frond, eventually there will be many. But you do need patience, months of it, if not years.

I only know this because a friend is a pot plant rescuer. If she sees a yellowed rose or a baffled begonia on a neglected shelf in the supermarket she will take it home and make it flourish. She has nursed many ferns back to health, too. I eventually asked for her secret, and here it is: 'I put them near a window and water them on Fridays.'

Now the secret is yours, too.