I had a little bay tree ...

I am hoping that you may be able to advise me on how to go about pruning a bay tree in my back garden. Our garden is a narrow town garden - just the width of our terrace house. The tree in question is right at the back. I planted it 18 years ago as a small cutting and it is now approximately eight metres tall.

I like the bay tree. It is lovely and provides shelter for birds in winter and nesting places in summer. It acts as a windbreak so there's a nice, sheltered place to sit at its foot. But it grows bigger and bigger and blocks out the light for the adjoining garden. Last summer I got an estimate from a garden maintenance person to come and prune it in August, but he never turned up to do the job. This year I asked someone else. He said that it was a winter job and that all the branches should be cut right back, so I would end up with just a skeleton. I do not think that I want my winter garden to look miserable with a skeleton of a tree at the back. Can you tell me when the job should be done and how it should be carried out?

Hanne Westergaard's bay tree is, as she says, lovely. Nobody has ever told it that it's not supposed to be hardy enough to survive in Sheffield. It has grown at an extraordinary rate since she planted it, and has waltzed through Yorkshire winters without a hiccup. She estimates that it is about 25ft tall and it shows no signs of stopping there. I don't know of any taller ones in Yorkshire (and would be glad to hear of any) but at Kingston Lacey in Dorset there's a bay 48ft tall and even bigger ones flourish in Margam Park, near Port Talbot, West Glamorgan. Mild coastal areas suit it well.

But so, evidently, does Ms Westergaard's garden, which is a narrow, wedge-shaped plot on the inside curve of a crescent. The bay tree sits at the bottom of the garden, the thin end of the wedge, growing as a tall, dense spire, with branches right down to the ground.

Ms Westergaard has trimmed the sides of the bay fairly regularly, so the tree has become like a big piece of topiary. But now her ladder runs out way before the top of the tree and she worries about how she can manage it in the future. At least 8ft-10ft will have to come off to bring the top of the bay back within reach of Ms Westergaard's shears. I suggested that she put her ladder up against the tree and marked the height at which she would like to maintain the bay in future.

This rather drastic topping will spoil the beautiful, tapering cone shape of the tree. Perhaps the best way round this problem will be to rethink the shape, and clip it in future as a cylinder rather than a cone, cutting the sides up straight rather than on a sloping line.

Ms Westergaard was happy about this change of line. She had seen and admired bays clipped as cones and cylinders in the Botanic Garden at Copenhagen and could see such a shape fitting well into the space at the bottom of her own garden. She is Danish herself, but has lived with her English husband in this Sheffield house for the past 20 years.

The top will look bare and awkward for a while but, like yew trees, bays are tolerant of hard pruning. Leaves will grow again from the bare wood, but the recovery is quite slow. The best way to treat bay is to trim it lightly but regularly during summer, rather than to give it an occasional but very heavy pruning. If you trim the tree regularly, you encourage it to form the solid, tight mass of green foliage that makes it such a good lollipop tree in a tub.

Like Ms Westergaard, I wasn't mad about the idea of the whole tree being chopped back to a skeleton, as one contractor had suggested. Much too drastic. When yew hedges are given this treatment, only one side of the hedge is done at a time, with a break in between to allow the yew to get over the shock. But her contractor was not suggesting even this nicety. The tree might have recovered, but it would have been asking a lot of it. Especially if, as it was standing there naked and shivering, Sheffield suddenly turned nasty and dumped it into the middle of a long, hard winter.

So when should this painful beheading take place? Not before August and not after the end of October, I would say. If you were taking similar drastic action in reducing a deciduous tree, you would wait until after leaf fall before beginning work, and you would want it done before the sap started to rise again in February. But evergreens, such as the bay, work to a different clock.

Ms Westergaard seemed worried about the competence of the people she had so far been in touch with about her bay. I suggested she should get contact the Arboricultural Association, which could recommend a qualified tree surgeon in her area. She cares about the garden very much. It was all concrete when she and her husband arrived, with cement washing up around the trunks of the three cherry trees that were the garden's only plants. Those came out. So, with more difficulty, did the concrete.

Ms Westergaard persuaded the corporation's road-sweepers to dump their loads of autumn leaves on her front garden. Then she carted the leaves through the house into the back garden to enrich the gravelly soil. She also got some old paving stones from the council and laid those to make an informal path down the centre of the garden, leaving plenty of room for planting on either side.

There's a stone wall down one side of the garden and larch-lap fencing on the other. Both are swathed with climbing roses, pyracantha, clematis and an extraordinarily pretty little climbing tropaeolum, T tuberosum, at its best now with spurred nasturtium flowers of orange, hooded in red. A 'Gloire de Dijon' climbing rose had taken itself up into the stratosphere, tangling with pyracantha around the back door of the house. What you looked at on the fence was not roses, but gnarled, thorny stem. "While you're here ..." said Ms Westergaard.

In the next half hour we hatched a drastic rejuvenation plan for the rose, as well as a hatchet job on the pyracantha. Meanwhile, a frog watched us with beady pop eyes from his berth in the little pond on the left of the garden path. He's not going to like these changes at all.

The Arboricultural Association is at Ampfield House, Romsey, Hampshire SO51 9PA (01794 368717).