Every colour except tartan

It is Scotland and it is rhododendron time again. Everybody who loves them will be trekking to the west coast where some of the richest collections in Britain grow. And just about every Scot feels an obligation to grow at least one.

My own relationship with them veers from being madly in love with individuals to loathing them en masse. Huge tracts of our land are now covered with terrible assemblages of magentas, purples, undergarment pinks; scenes calculated to damage the retina and spawn a myriad terrible postcards. So why us?

Rhodos really do like our climate, especially that of the west coast, where the high rainfall and the acid soil suit them (and which they also find in parts of Devon and Cornwall). What makes Scottish rhododendrons special, though, are our cool summers. Rhododendrons hate being baked.

We also have some exceptional collections. From the 1850s, a Mr Hooker, a Glasgow man, sent home endless marvels from the Himalayas, not only to the Royal Botanic Garden at Edinburgh, but also to the great gardens of the west coast (Castle Kennedy is a dramatic example, still with many of his introductions.)

What gardeners gradually realised was that it was an enormous genus of plants, encompassing shrublets only six inches across, to trees 80 feet high. The species that comprised it were also themselves often variable. British botanists, working from limited herbarium material, commonly described as separate species plants grown from the same seed pod. Soon, there were huge numbers of species names and no biological basis.

Hence the "Rhododendron Wars". These, waged with some passion, were between American growers (and Scottish supporters) who followed the entrenched but inefficient 19th-century classification, and the British growers (mostly members of the Royal Horticultural Society's rhododendron group), who followed the new Edinburgh-based and very much simplified, one.

We also have a considerable density of great rhododendron gardens, and in splendid settings. Though you can find most of the species scattered through English gardens (Windsor Great Park has an excellent collection), you need to travel much further to see them all.

Of course, it is the sheer diversity of rhododendrons, and the brilliant colouring of their flowers, that makes many of them such a menace in the garden. With about 1,000 species, once hooked, it is difficult to stop collecting; 19th-century growers were dazzled, too, by the ease with which hybrids could be made. They crammed new plants in.

Events combined: Sir Walter Scott; industrial boom in the South; cheap land in the North. Every Victorian with a bit of spare change wanted, and bought, an estate in Scotland. Arriving, each thought our gaunt, tawny, misty, silvery, hills needed a dab of colour. What better than a rhododendron? Two?

But what was, a century ago, an innocuous twig with a garish bloom, is now an immense cow-pat of shrieking colour, probably visible from Mars.

Any rhododendron, by itself, has beauty. Add another, too close and unconsidered, and you can have a clash. If you have the right acid soil, and the right climate, ensure enough greenery is between them to keep the colours cool. With such a palette to choose from, it is surprising that no gardener seems yet to have done seriously colour-co-ordinated plantings.

Among the undeniable beauties, where flower and foliage are in perfect balance, are some of the marvellous tender species and varieties. Best, to my mind, are exquisite and perfumed plants like `Lady Alice Fitzwillliam', and `Princess Alice', plants that associate well with chipped oriental garden pots, and whose soft white flowers have a smell that goes well with woodsmoke and disguises ancient labrador. If you garden somewhere chilly, grow them in shade and outdoors for the summer, then bring them inside before the first frosts.

Other good "rhodos" to treat in the same way include glamorous ones such as Rhododendron Lindleyi, which will go up to 10ft, and has large lily- shaped flowers, heavily perfumed, in May or thereabouts.

Or try R. formosum, with gorgeous white flowers that have a yellow blotch and a strong fragrance (its variety `Inaequale' smells the best of any). And if you must have colour, try the rose flushed R. horlickianum. Most of these are listed in the catalogue obtainable from P A Cox, Glendoik Gardens, Glencarse, Perth PH2 7NS. One of the most interesting collection of rhododendron species is at Blackhills, by Elgin, Morayshire. The garden is open on the last two Sundays in May, but ring John Christie (0343 842223) before a visit. He says Rhododendron sinogrande should be flowering well.

But do visit our other gardens. There are some quite magical remains, of 16th- and 17th-century gardens. There are even some old Scots garden plants that survive, especially fruit trees.

From the early 19th century, Scots collectors sent back to Scottish (and English) gardens, endless wonderful plants: shrubs such as forsythia, weigela, ribes, endless camellias, roses, neillias; herbaceous plants such as hostas, asters, lilies, penstemons, primulas; bedding plants like lobelia and verbena.

And, of course, wonderful trees like sequoia, western hemlocks and even, regrettably, the parents of `Leylandii'.

For romantic remains, try the King's Knot beneath Stirling Castle's cliffs, or Lincluden, with its magic and motte intact inside the outskirts of Dumfries. Or the south-facing rock-cut ledge that once held the garden of Castle Campbell near Dollar. But, most romantic of all if you ignore the modern parterre, visit Edzell Castle, where the grim walls enclosed Sir David Lindsay's paradise, which was once loud with birdsong and the drone of bees.

If you want to see what flowers that our long summer days, cool and moist, can produce, visit the lovely borders at Malleny House, just outside Edinburgh, or the great border at Crathes Castle in Aberdeenshire. Or try something more cottagey at Kellie Castle in Fife (best in the evening, and still open, once the castle has closed to visitors), or the enchanting little garden found at Broughton House, in the centre of Kirkcudbright.

Visit, too, some of our extraordinary range of nurseries. They produce not just rhododendrons and `alpines'. We have ones specialising in orchids from Madagascar, in bamboos (Scottish Bamboo Nursery, Middlemuir Farm, Craigievar, Aberdeenshire), in violas (Elizabeth MaeGregor, Ellenbank, Tongland Road, Kirkcudbright DG6 4UU), and in connoisseurs' plants (try Craigieburn Classic Plants Craigieburn House, by Moffat, Dumfriesshire DG 10 9LF, and Michael Wickenden, Cally Gardens, Gatehouse of Fleet, Castle Douglas DG7 2DJ - open weekends only ).

There are a number that specialise in interesting specimen shrubs; try Dobbie and Co, Melville Nursery, Lasswade, Midlothian EH18 1 AZ.

If you plan to visit, get a copy of the Scotland's Gardens Scheme book from: the General Organiser, Scotland's Gardens Scheme, 31 Castle Terrace, Edinburgh EH1 2EL. lt costs £3, including postage.

Anna Pavord is on holiday