Gardening: The basement that became a bower: It began with the drains flowing the wrong way, and it ended in a small paved area packed full of leaves. Anna Pavord tells a tale of disaster that has a happy ending

Drainage is not a sexy subject. It is one of life's greyer areas, like the workings of the Inland Revenue. You just hope you never have to grapple with it too closely. I only did once, when No 2 child was about four years old and posted enough extraneous items down the lavatory to gum up the entire system.

The local plumber came to the rescue and retrieved an impressive number of objects from one of the drains. He found trees, gates and several cows from a model farmyard, a small stuffed cat, a sock, two doll's dresses and enough Lego to build a simulation of the Taj Mahal.

Why had she done this, I asked our daughter. To see where they came out, she replied. Now you know, I said. Fortunately, the exercise was conclusive enough for her to be able to tick off drains as a subject of inquiry. And I, too, had learnt something about the subterranean geography of our house.

Given the vital nature of drains, it is odd that when you move into a house, you know so little about them. What happens to the rainwater coming off the roof? Where does the water in the side passage go when there is a thunderstorm? Under the back door, I have usually found, but our houses have not been noted for their convenience.

And what about basements? Potential swimming pools, you would have thought, without some fancy drainwork underneath to carry the water away. A slight slope in the right direction is equally important. Unfortunately, Pauline Barker in York had a slope in the wrong direction and found the water from her front semi-basement quietly slinking under the floor of the sitting- room inside.

Her house is in a pretty Georgian terrace, built of dun-coloured brick in four levels, including the basement, with chimneys marching in rows over tiled roofs. Like the rest of the row, it has a small front garden with steps up to the front door and steps down to a small semi-basement area, no more than 14ft x 7ft. Here there is another door leading into the sitting-room where the water wanted to be.

Mrs Barker's solution was to dig up the concreted area outside and make a drain pointing in the opposite direction, out towards the rest of the front garden. The work gave her the opportunity to replace the concrete with a more pleasing brick floor laid so that water drains towards the centre to disappear through a grating into the pipe.

The house faces roughly south and so the front gets more sun than the basement yard at the back. Mrs Barker put up hooks for a hammock in the front basement and filled it with pots. It has become one of the best bits of the garden.

The steps to this basement do not lead straight from the garden level to face the door. They come down on the wall opposite the door. This makes an important difference to the space. As you come out of the lower level door, the steps are not gaping at you, saying 'Escape]' You emerge into a space that is immediately full of leaf, the steps well disguised with pots on the opposite wall.

Everything that grows here is in pots. There is no bare earth to plant in. But Mrs Barker has always had a weakness for pots and brought most of the present collection with her when she moved up to York from Stockwell in south London six years ago. There are a couple of chimney pots, good for confined spaces, low pans of house leeks on the steps, stout tubs of rhododendron and camellia.

'Because I've been used to a much bigger garden, I tend to buy things that grow too big,' she said, but provided you have a series of retirement homes where you can send your plants as they outgrow their space, this is not necessarily a bad thing. Worse, in a tiny garden, is to have only minuscule plants, dots in a desert, with nothing bold or luxuriant to clothe the area.

Camellias are a great favourite and work well in pots, as long as you grow them in the sort of compost that does not turn their leaves yellow. Mrs Barker gives hers regular doses of Sequestrene and the foliage stays dark and glossy, a good background for later, more ephemeral summer displays.

A red-flowered rhododendron in a tub is also as important for its foliage as for its flowers. It is one of the Yakushimanum hybrids which make compact, rounded plants, ideal for life in a pot. The leaves are neat and narrow, backed with a dusting of ginger.

There are fuchsias, ivies, pansies, marguerites which you expect in pots. And dahlias and iris, which you don't. Thyme and campanula fiddle around in a small, sunny trough. There is even a yew tree in a pot that it shares with regale lilies. By the side of the door is an euonymus, with a mop of variegated leaves on top.

Because this is only a semi-basement, and because it is on the south side of the house, it gets plenty of light - even sun. More difficult are those areas where only minimum excavation separates the basement from the ground-level garden above.

There is not sufficient room for a separate terrace and the window looks out on to a dank slope of earth and rubble that seems as if it might slide inside on to your lap at any moment. Because of the lack of space between the slope and the house, these patches may catch the sun for only one delirious hour around the summer solstice. Given these conditions, a plant can look as happy as an injured oyster.

Fortunately, this is not true of all plants. Ferns actually choose these sort of billets in preference to anything else and they would be my first choice in planting up such an area, to give pleasure looking from the inside out. That is the only vantage point you will get on such a piece of ground.

You need reasonable soil for ferns, with enough humus in it to retain moisture, for ferns like damp feet. See to the soil before you think of plants and work through the patch, taking out any great chunks of clinker and concrete and substituting some bags of well-rotted manure well mixed into the soil.

As for plants, you would not want anything too tall so close to the window. Harts-tongues (Phyllitis scolopendrium) would be ideal because of their broad, strappy, evergreen leaves. Use them together with some of the lacier kinds of ferns such as dryopteris and the unusually meaty variety Polpypodium vulgare 'Cornubiense'. This has the useful habit of pushing out its fresh fronds late in the season, when everything else is looking tired.

With the ferns use hostas, not big bossy ones but quiet ones with small, lance-shaped rather than paddle leaves. Plant snowdrops in bold groups under the ferns, together with scillas.

Make mounds of cyclamen, both the autumn flowering C. neapolitanum and spring flowering C. coum. Try the handsome hellebore H. foetidus 'Wester Flisk'.

(Photograph omitted)