Winter wonders: Anna Pavord visits a Sussex garden so full of life that not even a flood can put it off its stride.

February can be a treacherous month, but each year it produces at least one day when the wind drops, the sky clears and the temperature nervously hauls itself up into double figures. Gardeners have learnt not to trust this apparent truce, this first glimpse of spring's white flag, but we can at least enjoy it while it lasts.

I was at Mitchmere Farm in Sussex, looking at snowdrops, on the miraculous day when for the first time this year, I felt the sun warmish on the back of my neck. The house, Edwardian red brick, sits in a fold of the Sussex Downs and faces south with a view of beech trees breaking over the crest of the hill opposite. Bantams fiddle about in the yard and along the grassy banks of the stream that charges through the garden. The water is so clear you can see every flint on the stream bed.

The stream comes and goes as it pleases, explained Sue Edden, who came to Mitchmere more than 15 years ago. This winter it has behaved beautifully. In the winter of 2000-2001, when flooding in nearby Chichester made the national news, the stream got above itself and the whole garden was under water from November to March. She has become an expert on plants that will survive floods. Surprisingly, one of them was Iris unguicularis, the Algerian iris, in full flower now in the Edden's yard. We're told, as gardeners, to give it the driest, hottest place we can find in our gardens. And yet it hung on here for five months, submerged under water, while cherry trees keeled over and yew hedges drowned.

It was a pity about the cherries, observed Mrs Edden, because she'd gone in for them in a big way. Fortunately, the orchard of apples and pears recovered, as did the double line of field maples, planted for shelter from the southwesterlies that roar up the valley. Hawthorns survived. So, less surprisingly, did the dogwoods and willows planted along the banks of the stream.

The pond the Eddens had made turned itself inside out in the floods, as springs full of air bubbles rose up underneath the butyl liner and pushed it up above the water, like a hippo wallowing. I looked at the photos the Eddens had taken during that cataclysmic winter. It seemed extraordinary to me that the pond could ever have been put right. The two greatest dangers, said the man who had supplied the liner, were UV light and cats, both of which in different ways could damage the fabric. He advised the Eddens to cover the whole thing with old carpet until the flood subsided. There was plenty of sodden, muddy carpet to hand that winter and the trick worked. Gradually, through a pipe wiggled carefully under the liner, Neil Edden vented the air under the butyl and as the floods subsided, so did their pond, liner intact.

The real difficulty for gardeners here is that winter wet is followed by an equally trying period of summer drought. The garden at Mitchmere is made on chalk and gravel, which drains like a sieve when the winterbourne - a temporary stream that is a feature of chalk downland - decides to disappear underground for the duration. Bulbs, of course, love the fact that the ground is well-drained, but how did they survive the floods, I wondered?

Fortunately, the biggest spreads of dwarf bulbs are under an old horse chestnut and a walnut, which stand on slightly higher ground towards the back of the garden. Here, in a magical carpet under the trees are snowdrops, aconites, one or two clumps of dark dwarf iris and thousands of Crocus tommasinianus. The snowdrops have been carefully spread about by Sue Edden, who splits and replants some of the largest clumps each year, just after they have finished flowering. The crocus, which came in a single clump from a friend soon after the Eddens arrived at Mitchmere, have seeded themselves about with gusto and show an extraordinary amount of variation.

The original clump was the mauve blue colour that you expect from this early little crocus, tight-furled, determined. But its progeny have branched out into pinks and purples, cream, deep blue and a wonderful dirty brown-pink with silver on the backs of the petals. Was I jealous? I should say so. I wanted those crocuses very badly indeed, because I've fought for years to get them going in just the way that Sue Edden has. Mice and squirrels beat me every time. Only in one small patch of gravel round a mop-headed bay tree in our new garden does a pink form of Crocus tommasinianus seem to be surviving - increasing even.

In Mitchmere, spread under the horse chestnut, the snowdrops were mostly our native Galanthus nivalis. Elsewhere in the borders were great drifts of G. 'Atkinsii', earlier into flower, taller than G. nivalis and altogether a brilliant garden plant. It's named after a Quaker nurseryman, James Atkins of Northampton, who died in 1884. In a top 20 survey of snowdrops carried out by The Plantsman magazine, G. 'Atkinsii' came equal fifth, alongside 'Bertram Anderson' and G. plicatus 'Wendy's Gold'. I'd put it higher, but I don't share the true galanthophile's obsession with yellow touched snowdrops.

Top of the poll was the snowdrop'S. Arnott', which commemorates Sam Arnott, Provost of Maxwelltown, Dumfries and Galloway, in the 1920s. Galanthophilia (people are now paying 100 a bulb for new, distinct cultivars) is not a new obsession. The Edwardians had it too.

Mitchmere

Farm Stoughton, Sussex PO18 9JW, 023-9263 1456, open tomorrow (11am-4pm), admission 3.

Other gardens open this weekend for displays of snowdrops and winter bulbs include:

Sherwood

Newton St Cyres, Devon EX5 5BT, 01392 851216, open tomorrow and 25 Feb (2-5pm), admission 2.50

Little Cumbre

145 Pennsylvania Rd, Exeter, Devon EX4 6DZ, 01392 258315, open tomorrow (12-3pm), admission 3

Bramdean House

Bramdean, Hants SO24 0JU, 01962 771214 open tomorrow (2-5pm), admission 3.50

Little Court

Crawley, nr Winchester, Hants SO21 2PU, 01962 776365, open tomorrow, Mon and Tue (2-5.30pm), admission 3

21 Chapel St

Hacconby, Bourne, Lincs PE10 0UL, 01778 570314, open today and tomorrow (11am-5pm), admission 1.50

Ivy Croft

Ivington Green, Leominster, Herefordshire HR6 0JN, 01568 720344, open Thur (2-5.30pm), admission 2.50

Benington Lordship

Benington, Stevenage, Herts SG2 7BS, 01438 869668, open daily until 25 Feb (12-4pm), admission 3.50

Myddelton House Gardens

Bulls Cross, Enfield, London EN2 9HG, 01992 702200, open 25 Feb (12-4pm), admission 2.40

Cambo Estate

Kingsbarns by St Andrews, Fife KY16 8QD, 01333 450313, open daily (10am-4pm) until 15 March, admission 3.50

Lacock Abbey

Gardens Chippenham, Wilts SN15 2LQ , 01249 730459, open today and tomorrow (11am-5pm), admission 2

Dolphins

Great Harrowden, Northants NN9 5AB,open 25 Feb (10am-4pm), admission 2

Pembury House

Ditchling Road, Clayton, nr Hassocks, Sussex BN6 9PH, open Tue, Wed, Thur (11am-4pm), admission 2.50