Gardening: Putting a bower in apple pie order: Anna Pavord has the plans and the place; now all she needs is Eddie to turn up and do it

OUR HOUSE ought to have a blue plaque on it saying 'Saved by Eddie, 1974-93'. Eddie filleted new pieces of wood into the old window sashes and patched new bottoms on the doors. He straightened the roof timbers of the house and divined the geometry of the drains. He surveyed a random collection of ancient fretwork strewn around the front of the house and magically turned it back into a porch. Now, after 18 years, the house is more or less upright and, miraculously, on the dry side of wet. For the first time, rather than being driven by necessity, we can choose our project for the year: central heating or an apple bower. Actually, there never was much of a choice. We just put central heating on the agenda to create the illusion of being practical. The budget gave us a wonderfully practical reason to knock it off again.

So, some evening soon, the phone is going to ring with news of Eddie's arrival to create the bower. To see how it is going to work (of course it may not) you have to imagine the kitchen garden running away from the house on the north side. The original paths divide it like a noughts and crosses grid, making nine squares, roughly equal in size.

I want to cordon off the central square, making a small room inside the bigger room of the kitchen garden, with some form of screen round three sides of the square. The fourth side, the south, would open on to a rough larch pole pergola that is already in position.

Treillage in this garden would be ludicrously out of place, and anyway, we could never live up to it. I haven't got the right clothes. You need a wide straw hat to go with treillage and something floaty around the legs.

I was thinking of a simpler arrangement of posts strung round with parallel wires, perhaps nine inches apart. The wire would support screens of cordon apples, planted slanting in opposite directions so that they made a living diamond-patterned trellis.

Cordons are a lot of work, as you have to prune them rigorously to confine the growth to the single straight stem, but I so enjoy the spectacle of trained fruit trees that this work would be no hardship. It would also be some time before growth was sufficiently advanced to make a convincing screen round the square. But there is no particular hurry.

The posts would probably need to be at least four inches square, and the edges chamfered (symmetrically bevelled) to finish them off. There should also be a simple finial on the posts, the sort you get on iron railings, to make a decorative flourish along the top of the screen.

If the wood is pressure-treated with preservative, it should last reasonably well. We may use some device such as Metposts to anchor the timbers in the ground. Posts seem to rot first at the base and these protective iron collars slow the process down considerably.

Another consideration is the final finish of the posts. I think some form of stain will be the least obtrusive. Paint is too self-conscious, plain wood too stark for this particular venture. With staining you get a hint of colour, but the grain of the wood still shows through. A dark blue-green might be just the thing. Good with the apple blossom.

The reason for this particular screen is to protect and disguise a collection of plants that do not fit easily into the rest of the garden: spiky agaves, cotyledons, aeoniums, all growing in pots. The best thing, probably, will be to get rid of the grass altogether and cover the floor of the square with gravel. Buff will make a far more fitting background colour for these desert plants than green.

A screen creates the illusion that you are entering a different world, but because it is not solid, you do not feel that the one world is entirely divorced from the other. From outside the screened area, you catch only glimpses of what is going on inside, and when you are inside you are still aware of the wider landscape of which this small enclosure remains a part.

The screen is a useful device for dividing up a long, thin garden. It gives you spaces that are easier to work with, and also creates separate areas that can be commandeered for different purposes. It is good to have a sitting-out area and a decorative scheme that you can look on with pleasure from the house.

Children need wilder, less structured areas that they can mould to their own purposes and do with as they please. Our youngest daughter spent much of her childhood halfway up a beech tree just the other side of a broken-down stone wall. The wall appeared to be important. Climbing over it, she entered a world of her own devising.

Round about one o'clock, if the weather was fine, there was usually a basket (my job was to fill it) hanging down from the tree on a piece of rope. Rustling up lunch was beyond even her considerable gifts.

By using a screen to mark the end of structured, adult territory, you can create this illusion of a different world beyond. This need not necessarily be for the sake of children. It could mark a change of style in a garden, leading from a formally planted area into a wilder, more informal layout with fruit trees growing in longer grass. It could signal a change of colour schemes, leading from cool to hot. It will always introduce an element of surprise, for there is nothing more intriguing in a garden than not being able to see it all at once.

The style of the screen will depend entirely on the overall setting of the garden. You can make a simple screen like a one-sided pergola, using larch poles for uprights and horizontals, bracing the joints with diagonal poles in between. This can be very effective swamped in a cluster-flowered climbing rose such as 'Seagull' or 'Rambling Rector'. Vines, wisteria and clematis also work well together.

The advantage of this type of screen is that it is relatively inexpensive and easy to cover with plants, but in town gardens the faintly rustic Thirties aura of such a construction may be inappropriate. Here, especially where gardens are paved throughout, something more architectural may be called for.

Tony Christie and Mark Barnett make handsome trellis screens in five different patterns, square lattice, two sorts of diamond lattice, a faintly Japanese design of close uprights and wider spaced horizontals and a modern design of one-way bars, which can be used horizontally or vertically.

Their screens are made from pressure-treated Scandinavian redwood and stained in dark green, grey blue or brown. You can also get them painted, though this costs 15 per cent more. The panels are made up in a wide variety of modules so that you can work out countless permutations of swoops and curves. This may be a danger. The smaller the space, the less swoopy the trellis should be.

Further information from Lloyd Christie Garden Architecture, 22 Doria Road, Parsons Green, London SW6 4UG (071- 731 3484).