Cally ho!: A nursery in south-west Scotland transports Anna Pavord to gardeners' heaven

All my favourite clothes come from one shop that recently closed down. Disaster. I liked it because it was small, independent and filled with things that I never saw anywhere else. The clothes were, in the main, quite simply cut, but the fabrics were extraordinary: soft tweeds in indescribable colours, pleated wraps that the saleswoman handled like a magician. "You can do this and this and this," she would say, twirling the stuff round me at supersonic speed. By the time I got home I'd forgotten most of the tricks, but the beauty of the thing never wore off.

I liked the woman who ran the place too. She had strong opinions and the look on her face as I stepped out of of the changing room was always enough to tell me whether I should buy or not. "The trousers are perfect, but the top isn't right," she'd say, whipping another one from the rail. And for the cynics among you, no, it wasn't always a more expensive one.

Gradually, if you're lucky, you build up a collection of independent places where you like to buy things, because you know that the person supplying them shares some of your quirks and prejudices. You don't want to be over-lulled though. It's good to be presented with things you might, on your own, ignore.

Good plant nurseries seem easier to find than good dress shops (or it may be that I'm keener on looking for the one than the other). Word about Michael Wickenden and his nursery at Cally Gardens, Gatehouse of Fleet in south-west Scotland, reached me years ago, and last month I finally got there, with the agapanthus at their azure peak and vast heads of lacecap hydrangea glowing out between sharkskin leaves. It was every bit as good as I'd been told.

The nursery is set in a walled garden, at the end of a long track, and when you get there and let yourself in through the door in the exceptionally tall brick wall, you immediately feel you've left all the horrible things of the world behind. Inside are vast pots of leafy begonias and a banana (Ensete ventricosa) all grown, I learn later, from seed collected by Wickenden on his various plant hunting trips. You don't feel you are in a nursery at all, but in a huge and staggeringly beautiful garden.

The stock beds, laid out in 24 long parallel strips, are so established, so overflowing with plants, that the narrow paths between them have completely grown over. Four vast flowering squares dazzle with red monarda under the purplish stems of Crambe cordifolia, dark-leaved eucomis shooting up alongside magenta lobelia and monkshoods of the deepest possible blue towering over the rusty foliage of rodgersia. It's complete and utter heaven.

But when I catch up with Wickenden, he's slightly gloomy. He's in the sales area, hidden at the middle of the swirling garden, where the plants so outrageously liberated in the stock beds are captured in pots and lined out in neat rows, alphabetically arranged. Most are herbaceous perennials, in which the nursery specialises. Wickenden's idea, when he first came here more than 20 years ago, was that gardening people would like to wander about the garden and jot down ideas before deciding what to buy. "Now" he says, "people just want to buy what they've seen on telly the night before." "Nonsense," I reply. So we're off to a good start.

His real problem, surely, is time. The walled garden is 2.7 acres. Most of it is garden (there are wide borders under the walls on three sides with an orchard at the bottom). How can he maintain the whole place to such a high standard, and keep a nursery well supplied with plants mostly grown from his own seed, when there are only 24 hours in each day?

The answer is to drive himself harder than most of us would care to. He was chucked out of school at 16 – "best thing that ever happened to me," he says – and, much influenced by John Seymour and the whole self-sufficiency movement of the early Seventies, decided he was going to support himself by growing and selling organic fruit and veg. He put an ad in The Times personal column: "Wanted. Walled garden" and somewhat surprisingly found one in north Dorset. He dug the whole place by hand, joined the Women's Institute so he could sell his produce at their markets, and got the walled garden looking so good that the owners thought they'd like it back.

For a while, he worked as a jobbing gardener, cycling about with his spade (he still doesn't drive) until he went to Northern Ireland. There he eventually set up his first nursery, in a field by Strangford Lough, a place he still talks about with a kind of impassioned longing. But the owner of the field didn't want to sell and the dream of his own walled garden wouldn't go away.

Then from contacts at Threave, the National Trust for Scotland's garden nearby, he heard of Cally, which was for sale. Built in 1775, it once occupied 24 gardeners, and a later head gardener, William Pearson, talks of his staff looking after 2,000 feet of fruit wall, three acres of vegetables, three acres of orchards, a vinery 100ft long, a peach house that was even longer, special houses for oranges and camellias and 100ft of pineapple pits.

The vinery still exists, with the potting shed at its back, a delicious, darkish place, with swallows swooping in over the potting bench and a dampish smell of compost. This is the powerhouse, where cuttings are potted up, seed sown and the whole delicately balanced business carried on of producing enough plants to keep the nursery stocked. Wickenden reckons that there are some 3,500 different plants growing out in the garden. Of those, 300 or so will be available to buy at any one time, either at the nursery or sent out in spring by mail order.

The catalogue seemed to me a crafty mixture of excellent staples and things I'd never heard of, such as kalimeris (it's a bit like aster; white daisy flowers with pale yellow centres). But you can bet those things are there for a reason. We should hear of them – that's the Wickenden line. I've marked up plenty of things, including a lovely variant of Agapanthus inapertus, called 'Icicle', that Wickenden collected in the Transvaal (it involved a detour of 600 miles). Instead of the usual drooping darkish head, this has flowers of palest blue, each tube tipped with a rim of indigo.

Please help me convince Michael Wickenden that there are still gardeners around who love good, unusual plants. Visit the nursery (the best treat I've had all summer) or send for his catalogue. A new one will be out in November.

Cally Gardens, Gatehouse of Fleet, Castle Douglas, Kirkcudbrightshire, Scotland DG7 DJ is open until 27 September from Tue-Fri (2-5.30pm) and Sat-Sun (10-5.30pm). Admission £2.50, email info@callygardens.co.uk, or contact callygardens.co.uk (which includes pictures of the garden and plants). Send 3 x 1st class stamps for a catalogue, minimum mail order £15 plus p&p