Country & Garden: By heavens, when do you plant?

Should you sow by the light of the moon or plan according to the rhythms of the sun? Anna Pavord gazes skyward, intrigued

I tidied the duster box recently. Don't ask me why. I can only think that it was a way of putting off the more gruesome tasks that took me to the duster box in the first place: blackleading the grates, cleaning the brass. But as a symbol of the transitoriness of things, nothing could be more potent.

Take Shaky. There was a time when one of the children's bedrooms was a shrine to the pop star Shakin' Stevens. In the duster box was embarrassing proof of her obsession: half of a red sweatshirt, with "Shaky" emblazoned on the front. She must have been very young at the time (at least, that will be her excuse) because it is a very small sweatshirt.

The remnant of a hideously shaming dress was my own. Well, the Seventies were weird, but were they really this weird? And yet this dress, with its brilliant, psychedelic swirls of shocking pink, magenta and orange, was once the star of my wardrobe. Now it was one of the few rags in the box that actually looked better encrusted with Brasso than it did in its original state.

There is nothing more transitory than fashion. That is the point of it, that it moves on all the time. Clothes and pop stars are more at its mercy than gardens, though there have been some high-spirited attempts to subjugate gardening to the cause. The difficulty is that gardens won't stay where they are put. This is a nightmare for stylists. The only way out is to get rid of anything that grows, and spread crushed car windscreens where the grass should be. Crushed car windscreen is the gravel of the Nineties.

Transitoriness provides excitement and freshness in a garden. Sometimes it is a style thing, a craze for a certain colour, such as the brilliant blue that is in vogue in gardens at the moment. There are styles in plants. Hostas used to be stylish, but aren't any more. Hellebores are certainly stylish. So are certain sorts of primroses. Daffodils have never yet made the leap.

There is an inbuilt transitoriness in gardens, too, created by the ebb and flow of seasonal plants. Jasmine and viburnum have taken over from the summer's roses. New views open up as leaves fall from the trees. And each year gardeners introduce different plants into the garden picture, some of them perhaps never intended as permanent fixtures. Marigolds, for instance, flowered spectacularly among the beetroot in our vegetable garden this year. I enjoyed that show, but it is more fun to plan a different performance there next year than to repeat the old one.

But underpinning these fleeting effects in a garden is a foundation of enormous strength and stability. The resilience and timelessness of gardens, the slow growth of trees, the immutable change of autumn into winter and winter into spring, the consequence those changes have on plants - no one can garden and remain unaware of these. Indeed, they may be why we took to gardening in the first place.

Tapping into this underlying strength is one of the things that makes gardening important to me. This, of course, is not a conscious feeling. When I wander out through the back door to do some casual weeding I do not say, "Fancy that. I am part of the great diurnal round." I just get on with the job in hand. But while you are there, gazing at the silhouette of the mahonia in the dusk and the sun sets, bleeding across the sky with the savage intensity that only happens on winter afternoons, you feel a lot better than you do inside. Colder, but better.

I don't feel I have to burrow around in my subconscious for reasons to garden. Fortunately, nobody else seems to feel the need either. Psychologists and psychiatrists leave us alone with our happy mania. My own theory about this (you have to have a theory in the psych-business) is that the act of gardening itself is what keeps you out of the hands of the shrinks.

For some gardeners, the greater scheme itself becomes all-important. Instead of underpinning the calming chores of pruning and sowing and harvesting, it becomes the driving force of everything they do in the garden. Over Christmas, I puzzled over Gwydion's Planting Guide by JR Gower, which describes itself as "the definitive moon-planting manual". The guiding principle is not difficult to grasp. Root vegetables should be sown, planted or transplanted in a period that starts two days before a full moon and ends three days before the following new moon. All other fruits and vegetables should be sown, planted or transplanted in a slot that starts two days before a new moon and ends three days before the following full moon.

Now, you don't necessarily have to go along with these rules (which have long been a part of gardening lore), but at least you can understand them. JR Gower adds a further complication: signs of the zodiac. The beneficial signs for sowing and planting are Taurus, Cancer, Virgo, Scorpio, Capricorn and Pisces, all either earth or water signs. The trick, says Gower, is to get the phases of the moon working properly with the movements of the zodiac.

That means, according to the example he gives, that tomatoes should be sown between 14 January (22.04 hrs) and 17 (8.42 hrs) or 19 January (21.22hrs) and 22 (9.35hrs). I enjoy the thought of JR standing with seed packet in hand, waiting, when most of us are thinking about bed, for the hand of his watch to creep round to the 04 position.

Nick Kollerstrom's Planting by the Moon is a much fuller and better designed guide to the same subject, though still wonderfully arcane. There is a generous day-to-day diary in this book, with full instructions on the state of play up there in the heavens. On 5 January, "The Moon has reached its north node, which is usually a stressful time, but is quickly followed by the trine aspect, which is more harmonious. Work only in the afternoon." Oh! if only I could. Afternoons are so wonderfully short in January. But, dear Mr Kollerstrom, afternoon-only hours just aren't an option. Will a thunderbolt strike me if I dig compost before noon?

I do hope not, because I am intrigued (though not persuaded) by this book. It tells about cycles of the sky, and how the moon may affect fertility and crop yield. It explains the rhythms of the sun and sets out sensible principles of organic gardening. It includes a modern-day plan of work for a productive kitchen garden, which appears alongside its 18th-century equivalent, garden notes taken from Martha Bradley's The British Housewife, which was first published in 1756. "December is a dead season of the year for gardening," says the sensible Mrs Bradley. That's all the excuse I need to stay by the fire.

`Gwydion's Planting Guide' is written and published by JR Gower (pounds 3.75). It is available from the author at 11 Summerhouse, Orchard Cottages, Bove Town, Glastonbury, Somerset BA6 8JA. You can also buy the book from Counter Culture at BCM Inspire, London WC1N 3XX (01823 698895). `Planting by the Moon', by Nick Kollerstrom, published by Prospect Books, pounds 9.99