Gardens are minefields of snobbery and this year the subject of 'horticultural correctness' has been given an added edge by an arcane dispute between David Cannadine, the historian, and Nigel Nicolson, son of Harold Nicolson and Vita Sackville-West.
In his new book, Aspects of Aristocracy, Cannadine, who now teaches at Columbia University in New York, portrays Nigel Nicolson's parents as consummate snobs. And nothing better illustrated Sackville-West's hoity-toitiness, he argues, than her famous garden at Sissinghurst, which excluded 'bedint' (bourgeois) suburban flowers. Rhododendrons, for example, were out because they resembled 'fat stockbrokers, whom we do not want to have to dinner'. So were azaleas - 'Ascot, Sunningdale sort of plants' - and hybrid tea-roses.
Nicolson, in his column in the Spectator, angrily replied that these choices were nothing to do with snobbery. Sackville-West did not like flowers that took up too much room and had garish colours. He added: 'She avoided parallel rows of lobelias and geraniums for the same reason that writers try to avoid cliches. Their familiarity breeds tedium.'
Which, some may think, is just snobbish prejudice. Britain has always been fertile ground for horticultural disputes because the best of them, like this one, are based on class distinction, a field in which we still lead the world.
The pattern is the same as in other walks of life, such as foreign holidays: a particular plant or style of landscaping is taken up by fashionable folk, who then switch to something else when the masses follow.
In the 17th century, for example, tulip bulbs fetched enormous prices and the flowers were depicted in paintings and on expensive pottery. Now, the tulip's garish reds and yellows are symbols of handkerchief-sized front gardens in the inner suburbs, which probably have garden gnomes, too.
The hybrid tea-rose, with its vigour and long flowering season, was acceptable when it was introduced at the beginning of the century. But opinion formers now prefer the softer but brief-flowering 'old-fashioned' roses. And Christopher Lloyd, the veteran gardening guru, started a trend away from roses of any kind last year when he dug up the rose bed at his show garden at Great Dixter in Sussex. 'They're quite disagreeable and make a very spotty effect even when they're flowering,' he said.
Mr Lloyd will tolerate the rhododendron provided the 'Surrey suburban cliche' of a bed, where they are planted alongside azaleas and conifers, is avoided. But the rhododendron is frowned upon for environmental reasons as well as for its blowsy vulgarity. It harbours scarcely any birds or insects and in the wild - notably in parts of Snowdonia - it quickly overruns acres of landscape.
Rosie Atkins, editor of Gardens Illustrated, says: 'I was at a school where there were lots of rhododendrons and hypericums in very dreary Victorian plantings. I learned to loathe them. I suppose they're all right in their place - like in the Himalayas or those big gardens in Scotland - but in a small London garden they scream at you.
'You used to see a lot of them at the Chelsea show, because it comes at the right time of year. Those technicolour displays - they made you fall right back.'
Jonathan Tye, managing director of the Lea Rhododendron Gardens at Matlock, Derbyshire, thinks all this terribly unfair. He points out that he grows some 550 varieties and that they don't all come big and in bright colours. 'You can choose what size and colour you like. It's like women. Not every man has the same taste in women, but that doesn't mean one is better than the other.'
So what should you grow to keep in with the current orthodoxy? Go for subtle shapes and colours. Particularly recommended are silver-leaved plants, including lavender; wild flowers such as foxglove; small-bloomed and not too vigorous varieties of clematis; love-in-a-mist; true geraniums (not the buxom pelargoniums often given that name); and those hellebores whose flowers are so unobtrusive you could mistake them for leaves.
But plant them quickly - the fashion may have changed next year.