Gardening: Take a cutting, shed a tear, wave goodbye: Leaving a garden can be heartbreaking. Anna Pavord meets the creator of a magical oasis who must soon trust her plants to strangers

'THE HUSBAND I can understand,' said a friend relating the story of a neighbour who had recently abandoned her home to live with another man. 'But how could she leave her garden?' How indeed? With your own bits and pieces of furniture around you, a few books, you can turn any house into home. A garden is not so quickly stamped with your own mark. Nor can you shift plants with quite the ease that you can a bookcase.

Actually, the law says that you should not be shifting them at all unless you have specifically excluded them from the contract of sale. Plants in pots are fair game, but anything with its roots in the ground that you are selling belongs to the prospective purchaser. So do any garden buildings or ornaments that are equally well rooted.

The law would not be the first thing on my mind if I were leaving my garden, though. I would be thinking of the trees we have planted and whether they would ever be allowed to reach maturity. I would be worrying whether the new owners were pruning the wisteria, for it does not flower without a good annual chopping. I would regret the loss of the background to the children's growing up. Certainly, I would mind leaving the garden more than the house.

The more you put into a garden, the more difficult it is to relinquish it. The only cure is to move to a place that has even more potential than the one you are leaving. That thought has been sustaining Mary Anne Robb, who, by the middle of September, must say goodbye to her garden at Chisenbury Priory in Wiltshire.

For 12 years she has been pouring plants into this garden: roses and masses of clematis against the chalk and flint walls; astilbes, rheums and rodgersias along the mill leat carved out from the River Avon; tall primulas and giant hogweeds by the old pond in the meadow. Only last year she made a new gravel garden with a variegated aralia as a centrepiece, and surrounded it with succulent exotics grouped in pots.

It had not occurred to her that she, her husband and family would not stay at the priory for ever. Without the recession, they probably would have. Soon a banker, a non-gardening banker at that, will own her carefully planted borders, the vines trained along the front of the house, the ancient apple trees filled with climbing roses. How did she feel about that, I asked, sounding uncomfortably like one of the Sun's foot-in-the-door news hounds.

'I don't think it has hit me yet,' she replied. 'I've been propagating, of course, taking cuttings of particularly favourite plants, dividing some of the perennials and potting them up, but I do that anyway as I sell plants on my garden open days.'

'Which bits will you miss most?' I pressed on, feeling a complete heel.

'The corners,' she said. 'I think a lot of women who garden like fiddling around in small patches. I like the corners here and there are lots of them. I think that is what gives the garden its special feeling.

'But,' she said, 'we've at last seen a place we want to buy in Somerset. It has amazing potential for a garden. It is good growing country down there. Better soil than we've got here. I don't think we would get such late frosts there either.' The balm was already at work.

Yet, inevitably, there will be a hiatus before the new schemes now germinating in Mrs Robb's head achieve the superabundance that is evident at Chisenbury Priory. She plants recklessly. A whole border of Shirley poppies waves in front of the comfortably sagging greenhouse, the flowers the colour of tissue paper left out in the rain. This is the first thing you see because it is where you pay to get into the garden.

After that, you have no idea where to go. Great billows of roses and mock orange, forests of blue and white campanulas rise up to block off the longer view. If you stick to the path going towards the house you will come to what was once a stone-paved terrace, now almost totally obscured by self-seeded astrantias and alchemilla. There is a round pond here with a raised brick edge. Large pots of felicia sit balanced on the rim.

More pots sit on the parapet of the informal bridge that takes you over the mill leat below the terrace, a row of geraniums this time, all different kinds, all unusual. Then you find yourself in a meadow with a wide mown path leading down to a much wilder, larger pond. Tall spears of iris leaves separate the searingly orange flower heads of lysimachia.

As you walk through the meadow, you pick up the tile-topped wall that guards the inner garden. There is a narrow border along this outside edge, too - hollyhocks mostly, almost as tall as the wall, swaying stiffly over dark-blue pouchy monkshoods.

A small oak gate leads through into the walled garden. First you see the line of old espaliered apple trees and, behind that, the stream again, crossed by two small humpback paths, surfaced with flints. Masses of blue and white campanulas mat together under the apple trees. Clematis tips off the walls.

There is a duck on the stream, one of those that thinks he's a dog and follows you round the garden. He was raised by a chicken, explains Mrs Robb, and there are no other ducks to tell him what to do. He could, if he wanted, take a few lessons from the moorhens which paddle energetically up and down the stream, flicking the white feathers on their rumps. Instead he plods around on dry land, rolling from one flat foot to the other, not even quacking.

The duck came with me from the stream up over the informal terraces that rise up to the house, which is an extraordinary jumble of facades and building materials. If you follow quite close to the wall on the right-hand side you will come to one of Mrs Robb's favourite corners. You would miss it altogether were it not for an arrow in the border, bossing you along in the right direction.

This is a corner that used to be a compost heap, bounded on two sides by the chalk and flint walls that are such a gift to this garden. Now the floor of the little space is paved and a millstone, dug up in the garden, makes a plant stand for a wide pot of glaucous echeverias. Flowers in pots stand in a ring round the base of the millstone, like a ra-ra skirt on a heavyweight boxer.

The most formal part of the garden is approached through the new laburnum tunnel. This spreads over a wide flagged path that leads you round to the side of the house, where brick buttresses hold up the walls of one of the oldest parts of the building. At the front, wide herbaceous borders stretch down either side of the entrance court. Blue, yellow and purple are the dominant colours here, with delphiniums, more campanulas, catmint, artemisia, purple sage, grey onopordons and neat umbels of agapanthus. It is classic, beautiful, but easy to repeat. You can understand why Mrs Robb did not see this, the grand statement, as the part of the garden she would most miss.

The new owner-in-waiting of Chisenbury Priory had invited her to come back if she wanted to take more cuttings of shrubs during the autumn. And would she, I asked? 'No,' she said vehemently. 'Never.' Then a pause. 'Well perhaps not never. A garden is like your children isn't it? It's difficult to believe that anyone else will ever love it quite as much as you do.'

Chisenbury Priory, East Chisenbury, nr Pewsey, Wiltshire, is open

(2-6pm) every Sunday until the end of August and every Wednesday until 15 September. Admission pounds 2.

(Photograph omitted)