Mixing memory and desire: As April ended, a long-awaited spring came briefly to life. In his third seasonal essay, a leading nature writer finds hope in an Oxford meadow and at Greenham Common

IT SEEMED for a while as if it might never come. Since September we had been suspended in what felt like a perpetual winter twilight, a bitter, corrosive mixture of wet and wind that promised nothing except more of the same. March was indistinguishable from November. April was dark and missing until its final week. Then, almost abruptly, we had our spring, four days of sublime, southerly weather packed into a Bank Holiday weekend.

On the last day of April there were swifts cruising high over Wembley Stadium after the Rugby League cup final. On May Day, there was May blossom foaming the verges all along the M4 - the second year running it has been out from the start of its name month. In the centre of Bath on the holiday Monday, I saw speckled wood butterflies flitting among the august terraced gardens as if they were in dappled forest glades. When I got back to the Chilterns the following day the vegetation had run riot. Leaves and flowers that normally follow each other in orderly procession had burst open together, crab apple and garden lilac, cow parsley and sappy new beech foliage, the first horse chestnut candelabras swelling next to the last drifts of cherry blossom. On low ground even the oak and ash were leafing together - an unthinkable occurrence in weather lore. It was as if the entire landscape had been under a forcing frame.

And how we needed it. We were teetering on the edge of a mass pathetic fallacy, seeing the dismal weather as a reflection of the supposedly depressed and decadent state of the nation. Spring's business is to mark new beginnings, to purge gloom and self-deprecation, and we are in trouble when it gives us no signs to which to cling.

I still keep, for comfort, the rhapsodic essay that Jan Morris wrote on the gilded spring and summer of 1990, which she saw as a fitting farewell to the decade that had given us Chernobyl and monetarism and an appalling sequence of assaults on the natural world. The hot seasons that year were full of serendipity and romantic associations. Mandela had just been freed, the Berlin wall was newly down, and summer birds and prodigious insects swarmed through the halcyon days of May.

In July and August, a giant Caribbean turtle was feasting off jellyfish in the Channel, and Morris watched 77 pipistrelle bats fly out of their roost above the kitchen of her Welsh cottage. Those months, she wrote, were 'an allegorical moment of reconciliation; a window . . . through which all too briefly flickered a message that the worst might be over.'

Like the hopes of 1990, the brief spring of 1994 didn't quite come to fruition. It vanished as suddenly as it arrived. It was maddeningly condensed, with none of the slow, exquisite lightening, the savoured moments of imagined (or remembered) springs. I was away from the home patch for just a short weekend, and I missed two seasonal rites of passage to which I am sentimentally attached: seeing my first swifts of the year over the parish church from my study window; and walking in a particular corner of my own wood on the day when the young beech leaves unfurl over the bluebells - an experience that, with the sunlight filtering through the semi-translucent new leaves and the bluebells rippling underfoot, is like walking underwater.

Some years ago I came across a scientific conceit that made me feel less disconsolate about such lost moments. It was a measure of the advance of spring across the land, based on the average first dates at which common and widespread flowers first come into bloom. Different species flower at times determined by a combination of daylight length and temperature, and in general bloom later the higher and the further north they are.

So primroses come into flower a whole month earlier on the Devon coast than they do in the Cairngorms. As well as on the M4, May blossom will have been opening simultaneously on the Sussex Downs, on Pembrokeshire cliffs, and on warm wasteland in the industrial Midlands. The lines joining these points are known as isophenes, and from them it is possible to calculate that spring travels inland and north at a rate of roughly 2 mph. That is remarkably close to strolling pace, and I used to toy with the fantasy of following the spring on foot, like a guest behind an unrolling carpet. But as anything other than an abstraction, the idea is a nonsense. The surfaces of Britain are so minutely and locally convoluted that every half mile has a sunny bank or shaded frost-pocket that can move first flowering dates two weeks either way. It is possible to join up regional first dates into wavy fronts and contours, but at a parish level the isophenes would cross like a mad cat's cradle.

Yet tracking the spring is something I seem to have been doing compulsively since I was a child. By the time I was a teenager I had a personal timetable of the 'proper' arrival dates and spots for summer migrants. Now, when things ought to be stirring and aren't, I get as fidgety as a migrant bird myself. I check out favourite parish plants, scan the skies over lakes, beat the bounds of my own territory. It is a ritualistic business, doubtless bolstered by nostalgia, but including a good deal of real nervousness. Ted Hughes saw the annual return of the swifts and their first madcap races around the house-tops as signs that all was well with the world. 'They've made it again, / Which means the globe's still working, the Creation's / Still wakening refreshed, our summer's / Still all to come.' It's a heart-lifting image, but over recent years I have found myself increasingly troubled by the awful corollary that lurks between its lines.

What would it say about the state of creation if one year they failed to make it back? What if, one spring, leaves corroded by acid rain fell as soon as they had opened? That way lies real paranoia, which is why, when the spring is held up, with plants in suspended animation and birds trapped on the other side of the Channel, waiting for the wind to change, I go hunting for reassurance further afield.

Henry Thoreau, in mid-19th-century America, always walked westward, following the sun and the expanding frontier. 'My needle is slow to settle,' he wrote, 'but it always settles between west and south-south-west. The future lies that way to me, and the earth seems more unexhausted and richer on that side.' I am not sure that I share his transcendental views on rambling, but west is certainly the way you go to meet the spring.

This year, on the equinox, 21 March, I was working in Devon, close to the balmy valleys south-east of Dartmoor. The rain fell continuously, but the primroses were unbowed in the turf-banked lanes, and I decided to stay on for an extra day. It was not a sensible decision, and I made things worse by walking a route that I had driven over last autumn, when I had been amazed at oak woods clinging to sheer hills and corkscrew lanes like crevasses. On foot, the whole landscape seemed scaled down and the spring flowers along the lanes were in incongruous order - the wild daffodils past their best, the woodruff and archangel out before the bluebells were barely in bud. Perhaps this is their way down here, but added to the gales it gave them a touch of uncomforting foreignness.

As March slipped into a grey April, I began making more urgent forays at home. There were chiff-chaffs - the first warblers to arrive from Africa - singing in the woods, but little else. Our winterbourne, which had at least made something tangibly exciting out of the ceaseless rain, had slunk back underground. And, on top of everything, it was the first spring that our new bypass had carried traffic. I had learnt to live with the road itself, which had been threaded neatly between our local woods and wild spots. I had even enjoyed the building of it, which had taken on the character of a rather interesting natural disaster, a slow-motion earthquake, perhaps. I had forgotten about the cars. Now it was roaring, and I stood in the woody common where I had spent a good deal of my adolescence, shocked at my own ability to blinker out the future for the sake of present excitement.

Selborne, the Rev Gilbert White's village, offered no succour either. By the third week of April, a fortnight after their usual arrival, there were still no swallows in the village. I plodded the hollow lanes, worn deep into the sandstone by centuries of use, and found their flowers as disordered as those of Devon. And one of their most ancient landmarks had vanished. A patch of green hellebore, with vast jagged leaves and pea-green flowers, that had survived for more than two and a half centuries in the spot where White described it, had finally succumbed, buried somewhere under farm rubbish and collapsed bank-top trees.

Oxford, I hoped, might be a bit more reliable. I go there every April to see the fritillaries in Magdalen College Meadow - one of the most beautiful and extraordinary sights of springtime Britain. The snake's-head fritillary is the most darkly glamorous and exotic of all our native flowers. It is rarely more than 1 ft tall, with pale, grass-like leaves. But at the top of each stalk are suspended one or two crimped bell-flowers adorned with purple chequering. Close-to, the patterning becomes more complex, a mottle of lilac, plum and the rusty brown of dried blood, with the patches of colour laid over each other, as if they were scales. If you lie under a cluster of flowers, they wave in the wind above you like cobras' heads - and you will see yet another reptilian feature: between the pointed, jaw-like petals slip yellow and apparently forked stamens. No wonder fritillaries picked up a remarkable and suggestive array of local names. In the West Country they were lepers' lilies and Lazarus bells, because of the similarity between the shape of the flower and the bells carried by lepers - and maybe between the livid blotches of the disease and the mottle of the petals. They were toad's-heads in parts of Wiltshire, dead men's bells in Shropshire, snake's-heads widely across lowland England. Vita Sackville-West described them as 'Sullen and foreign looking, the snakey flower / Scarfed in dull purple like Egyptian girls.'

There have been writers who believed that they were foreign, an escape from cultivation, or a deliberate introduction into fashionably wild 18th-century estates. For despite their eye-catching flowers, and their habit of growing in tens or even hundreds of thousands in the damp hay-meadows they favour, they were not officially recorded in the wild until 1736. The Magdalen colony was not explicitly commented on until 1785, causing the botanist George Claridge Druce to sow the first seeds of scepticism about their origins 100 years later. 'It is not a little singular that the Fritillary, so conspicuous a plant of the Oxfordshire meadows, should have so long remained unnoticed by the various botanists who had resided in or visited Oxford.'

There is a possibility that the flowers were introduced here and there. But in most of their remaining sites in English river valleys they are growing in fields with unbroken histories as ancient hay-meadows. Many of the parishes where the flower used to grow had not just rich vernacular names for it, but annual festivals based on the plant. I think the failure to record it was confined to the botanical establishment - another episode of spring expectations gone awry. The plant grew largely in the kind of flat, wet, farming countryside that would not attract the average 17th- or 18th-century botanist. Its flowering period is short and fickle, and often in the coldest weeks of April. The botanists were by their firesides - or up more romantic mountains.

The fritillary is now reduced to a score or so of sites, having been all but wiped out by the ploughing, drainage and spraying of old meadows. But the Magdalen flowers survive, defiantly abundant, and were my first true taste of spring this year.

I drove back a circuitous way, via Greenham Common airbase in Berkshire. Since it was closed down two years ago Greenham has been going through a metaphorical spring of its own. The two-mile-long concrete runway is already starting to dissolve, leaching calcium into the surrounding grassland, which is beginning to sparkle with chalk-loving flowers, wild carrot, eyebright, even orchids. Natterjack toads lie up under discarded ammunition boxes. The cruise missile bunkers, Greenham's heart of darkness, have been colonised by bats. There is an even chance that Greenham may again become true commonland for local people and wildlife, which will make it a powerful symbol of regeneration and a real peace dividend. Late last summer I stood on that fearsome runway, the focus of so many communal nightmares, and watched swallows mobbing a family of young hobby falcons. So, on that warming April day, it was no real surprise to see, flitting over the thickets of razor-wire, my first swallow of the year.

It was a vanguard bird. Minutes later, as I was driving past Thatcham station, the air began to fill with swallows. They were strafing flies over the car park, drinking on the wing from the River Kennet and resting up in ever-increasing numbers on the telephone wires. More were materialising by the minute, dropping out of the clouds, until I counted more than a hundred. They had, I'm sure, just arrived after their Channel crossing, and I doubtless made a dreadful exhibition of myself welcoming them home.

That was 20 April, the first sign that the weather might change. The swifts arrived on the 30th, and by 3 May we were back in cool, wet Atlantic weather. Now it is mid-May, and I am walking in the high Chilterns, east of Watlington. There is a chill mist hanging over the hills, and it seems a day exactly in keeping with the drab procession of the past six months. Yet something has changed. In those intense few days at the beginning of the month, the landscape passed through its rites of spring. Now, despite the weather, it is in a different mode. The beeches are in full leaf, a fantastic luminous gauze that seems to glow against the mist. Troops of pure white, ectoplasmic slugs are crossing the lanes between the woods, bound on what business I do not know. There are swallows and house martins hawking for insects just inches above the pastures. And in the distance, heraldic above the ridge, I can just make out a soaring red kite, one of a population recently re-introduced here after the bird was wiped out across England by 19th-century gamekeepers. Life goes on in its own ways. The ordered, gentle march of spring is a human invention. For most species it is a convulsion, a time for the most urgent, compressed business of their lives. If this means they must fly by night, materialise out of the air, burst through concrete, find human help to reach new territory and complete the whole rounds of migration and pairing, leafing and flowering in a few days, then that is how it must be, even if we are not there to see it. Keats was right to say that 'It is a flaw / In happiness to see beyond our bourn.' It is also a flaw to hang so desperately on what is to come, and to fail to see survival enacted continuously under our noses.-