Hedge of reason: Whether it's there for practical reasons or pure aesthetics, a beautiful hedge deserves the very best treatment that money can buy, says Anna Pavord

Hedges are a new responsibility for me. Our old garden was bounded mostly in stone and though we planted some yew hedging there, we spent our time urging it on, not clipping it back. In our present garden, we inherited old field boundaries of blackthorn, hawthorn, bramble, holly and dogwood.

Previous owners had planted hedges of laurel and pyracantha. We added double hedges either side of a wide new walk, putting in a mixture of native species: beech, spindle, yew, holly, hornbeam and blackthorn. After only three years, they are already seven feet high.

I've also gone slightly mad on box hedging. That was a gamble, given the disasters of phytophthora, but the little bushes have been well fed and have plenty of air blowing through them. I've also avoided using weedkiller on the paths along which they are planted. So far, so good. The box has already reached the height we want (45cms, roughly 18ins), although the box balls which I grew from rooted cuttings still have a way to go. They are lined down one side of the new stone path through the flower garden.

Then there are the bay trees, lollipops on sticks, bought originally for a daughter's wedding, now lined out along the back of the flower garden. And we also planted a yew hedge to disguise a slightly ugly retaining wall between the yard and the garden at the front of the house. So, one way and another, there's a lot of clipping to do and late July or early August is the best time to do it. Nesting birds have fledged their young (and we seem to have nests in every direction - swallows have built on top of the electricity meter in a shed. Even the meter man thought it best not to disturb them ...)

Mechanical trimmers are the quickest tool to use, hand shears the safest. On intricate pieces of topiary, you may need the kind of one-handed shears that were used to shear sheep. I like hand shears and have just bought a new pair, made by Bahco (£35.99). They are light and the grips feel comfortable, but in the end, I chose them because my favourite small triangular bow saw is also made by Bahco. The blade of that doesn't wobble (a problem with some bow saws) and years later, it is still sharp enough to cope with anything I can cope with. If you are lacking brute strength, good cutting tools are an essential investment.

So, one by one, the hedges are being bashed into shape. Kevin, who works here a day a week, did the pyracantha hedge with his petrol trimmer, and I followed behind later, picking the cut bits out of the top. Pyracantha is by far the worst of the hedges to deal with because of its vicious spiky thorns. I loathe it. Fortunately, it seems to be dying out in patches, so gradually we're replacing it with bay, which we'll clip as a cloud hedge, billowy rather than straight-edged. In the southwest, bay is quite hardy. It would not be an option in colder parts of England, particularly where it was exposed to an east wind.

Berberis is equally unfriendly, but in town gardens, I like the privet that still edges the front patches of some Victorian terraced houses in places such as Hammersmith and Clapham. It's an entirely appropriate boundary for houses of that period. It provides a screen against the world outside, stops litter blowing into the garden and greens up a view that is often more sterile than it need be. Privet should be clipped now too, as should hedges of beech and escallonia. The dreaded xCupressocyparis leylandii is best clipped in May and June. Or you can hire a chain saw and demolish it entirely.

Yew has a name for being slow, but on a well-prepared site, this isn't so. New growth on our yew hedge, planted in March two years ago, is already 24cm (10ins) long and the hedge is five feet high. Usually, I buy cheap and small. On this occasion, since we only needed ten plants to complete the run, I splashed out and bought bushy plants, more than two feet high to plant at two feet intervals. Hopes Grove Nurseries, who have supplied all our hedging, sell them for £10.95 each - quite an investment, but worth it if you take care of the young trees. The ground needs to be well prepared (we dug in masses of compost) and for at least the first year, the trees need watering in dry periods, summer or winter.

The British natives we planted either side of the alley were much cheaper: 60 plants for £90, planted at 18in intervals. Hopes Grove, who specialise in hedging plants supplied those too. We've not yet lost a single hedging plant, though we must by now have planted two hundred. The first box hedge, planted behind the flower border has just been cut and because it has fleshed out, is beginning to do what we wanted - provide a clear defining line along the back of the border and alongside the path that runs between it and the boundary hedge.

The paths that criss-cross the bank stand out much more clearly, now they have their box edgings, than they did before. But you have to watch the plants inside the hedge. If they are too vigorous and start flopping over the box, the box is discouraged and dies back. This started to happen when a crambe got over-ambitious. But before I waded in to help the box, the crambe died. It must have guessed my intentions. I won't replace it. There are two others slightly further away that won't interfere with the hedge.

Flopping neighbours are bad for a hedge, but clipping is also difficult when there are too many things lolling in the way. The only plant now allowed to encroach on the box hedge behind the flower garden is Clematis durandii. It's a leaner, not a clinger and its arms are lightly leafed. The flowers are dark indigo blue. Another strand of this same clematis has been propped up against the head of one of the lollipop bay trees. Those too have just been clipped and won't need attention for another year. C. durandii needs cutting back hard (to within 18 ins of the ground) in February or March, so both box and bay get a breathing space and are not in danger of being swamped.

The only hedge that hasn't put on much growth is the one of native holly. Paradoxically, although I loathe pyracantha because of its prickles, I'm prepared to put up with anything for the sake of holly. We have some big old trees rearing up out of the boundary hedges and there are plenty more in the lanes around. So the conditions should be right for them. But the eight plants that went in at the same time as the yew (between 18 ins and two feet high, £3.49 each) to extend a holly hedge behind the new cold frames, are no taller now than they were at planting time. They are bright and glossy though. Some of them are even berrying. Perhaps that is why I respect them. They refuse to conform to our need for instant gratification.

Hopes Grove Nurseries, Smallhythe Road, Tenterden, Kent (01580 765600)