Do your sences a favour this summer and pay Derry Watkins' astonishing nursery a visit, says Sue limb. Photography by David Morrison

If you give yourself one treat this summer, it should be a trip to a special place tucked away just off the A46, seven miles north of Bath. It's called Special Plants and 'special' is putting it mildly. I first stumbled across Derry Watkins' flowers about 15 years ago in a packed plant fair. It was like the old song: Some enchanted morning, you may see a strange plant across a crowded room... Derry's blooms stopped me in my tracks. Blue daisies! Pink exploding stars! Rampant vines flickering with petals like tongues of fire... elegant weeping shrubs dripping with tiny dangly sky-blue bells... My mouth went dry. My heart began to thump. It was like suddenly arriving in a strange new country with a completely alien and seductive flora.

Iris Murdoch once said, "People from a planet without flowers would think we must be mad with joy the whole time to have such things about us." And Derry Watkins' approach is: "I need to be able to garden all year round in order to stay sane." But mad or sane, if you've ever been interested in a plant for a split second, a visit to Derry's nursery should result in a lifetime addiction.

Her nursery stocks plants she is currently intoxicated by, and once she loses interest in something, it has to make way for the next wonderful discovery, ("I am the least faithful gardener," she admits), so you won't find predictable trays of summer bedding here, or the kind of classic staples of the border available at every garden centre. What you will find are plants she has brought back from trips to South Africa, India, Nepal, Chile and Ethiopia, as well as refined and rare versions of familiar and much-loved classics.

Derry's life in botany is an unending voyage of discovery and experiment. Her plant lists and labels are not just informative, they reveal her affection and wit: if you stumbled upon the nursery and browsed for a while, you would first be amazed by such labels as "Tutankhamen's Pea - found in his tomb", "St Bruno's Lily", "The Ladybird Poppy" and "Moon Carrot". You would also realise that somebody very unusual was behind this exotic Eden. Plants are described as "obscene but charming", "startling", with "leaves like silver ghosts".

So who is this poet and wit, whose passion for her plants spills out even onto the normally mundane labels? She is an American who, as a child growing up in Connecticut, hated gardening, her mother's passion, and whose first experience of crossing the Atlantic brought her to Sligo in Ireland, where she attended a Yeats summer school at the age of fifteen. When she returned to Europe again after finishing her psychology degree, she briefly settled in Ireland - the idea was to work on a film script about Yeats - and this was where her love of plants began.

Derry rented a primitive cottage on a mountainside overlooking the sea ("I had to dig a hole for the loo"). It was surrounded by chest-high grass and she asked a neighbour to mow it for her. He broke his scythe on a circle of stones, which alerted them to the presence of a long-lost secret garden. Derry spent the summer rescuing plants from the strangling and choking grass, and when the side of the mountain got a bit too cold in winter, she returned to the USA with a love of gardening firmly planted in her soul.

Her next adventure was in America, where she helped a friend who was trying to establish "the word's best vegetable garden" from soil which was "ridiculously" rich. They were starting from scratch, though: a whole field needed digging, and friends and acquaintances were enlisted to help. "By the end of the summer," recalls Derry with a twinkle in her eye, "we'd found out the ones who were best at digging, and married them."

Her husband, Peter Clegg, had been studying Environmental Design at Yale and Derry returned to England with him so he could finish his degree in architecture. It was almost accidental that they came to the countryside north of Bath, where Peter had his first architect's practice. They initially only intended to stay a couple of years, and first put roots down in Marshfield, where Derry raised two sons and tens of thousands of cuttings and seedlings in a 40-foot greenhouse that ran the length of the south wall of the house ("Oh, how I loved that greenhouse! You lived and breathed it!") They stayed at Marshfield for seventeen years, and Derry took to the Cotswold landscape perhaps because its small scale, higgledy piggledy intimate hills reminded her of Connecticut.

Her first commercial venture was a stall at the local W.I. market, partly to ease the pressure on space in the greenhouse, but fellow plantaholics swiftly discovered her range of extraordinary and wonderful plants. She started organising plant sales for the NCCPG (National Council for the Preservation of Plants and Gardens) and when she found a great hall in Bath and thought it would be perfect for a botanical event, she founded the Rare Plant Fairs which have become a highlight of the summer for the green-fingered.

Twelve years ago Derry and Peter moved from Marshfield to their present site: an idyllic south-facing valley surrounded by dreamy fields, but also a formidable challenge. Their potential house was a derelict barn surrounded by four acres of rough land.

Peter designed the house and garden and Derry planted it and developed the nursery, and the fascinating progress of the project is recorded on her website: www.specialplants.net, where you will also find details of days when the garden is open - the next one is on August 21 - and the practical courses Derry runs. In September, for example, she is offering Taking Cuttings, Seeds and Seedlings, and Gravel Gardening, and there are several other day courses in October and November. The nursery is open every day in the summer season.

Derry doesn't do the big shows at the moment, though she did make a splash with a black and white exhibit at Chelsea one year, but she does lecture, attends numerous plant fairs and gives demonstrations. Sarah Raven described Derry's enthusiasm as 'Vesuvian' and when not erupting to enthralled audiences, she spends as much time as possible actually in contact with plants. Her current passions include grasses, because "they move, and in winter in low light they shimmer; evergreens are heavy but grasses are light, they never need staking, and they do their thing high up - but they do need space."

She also confesses to being "mad about umbels" - that's the cow parsley family, which includes Angelica Gigas ("amazing big purple domed flower heads") because of their elegance and restraint, and she has a keen interest in colour "I love weird colours - muddy colours - purply muddy grey - rotting meat colour!" she confesses, volcanically.

They do say that, during economic downturns, florists do well. It's as if, in dark times, we realise all over again the miraculous beauty of flowers. If you've just listened to the news, and it's depressing, here's a perfect way to cheer yourself up: get thee to a nursery.

www.specialplants.net Garden open August 21.