For much of the year, our troupe of sweet and Parma violets occupies a shady spot outdoors, berthed in assorted clay pots and pans filled with well-drained loam. Come winter, we move them to a cold frame or, in our current post-move chaos, one of those self-assembly mini-greenhouses. This isn’t essential for sweet violets, which are hardy enough to flourish in the open garden, but it is prudent with Parma violets, which loathe cold and wet.

Both kinds repay our kindness by flowering earlier than usual-now, in fact-allowing us to bring them indoors for a few days apiece just when we need them most. They look enchanting top-dressed with fresh moss. But it is their scent, cool and carnal, earthy and heavenly, sweet and sophisticated, that really decorates a room. No plant can vie with violets for dispelling gloom.

These manoeuvres are a small price for one of the most intense of winter pleasures. And yet, for the past 50 years, few have been prepared to pay it. Wartime austerity was followed by burgeoning exotic tastes; violets were marginalised and thought quaint. It wasn’t always so. In the 1870s, Toulouse alone was exporting 13,000lb of violets to London every February.

The British retaliated by devoting swathes of the West Country to their production, so giving The Clevedon Mercury a rare scoop-the near-suffocation of railway passengers by the perfume of violets in transit from Somerset to London. Once there, sneered The Gardeners’ Chronicle, they were snapped up ‘by thousands of City clerks’. But violets were still good enough for Queen Victoria: each year, 3,000 pots were grown for Her Majesty at Windsor.

Many of those plants were rooted in more distant royalty. In 1816, Isaac Oldacre, gardener to Tsar Alexander, returned to Middlesex bearing the Russian violet, Viola suavis. By the mid 19th century, it was being crossed with our native sweet violet, Viola odorata, spawning a new generation of hardy perennials: large-bloomed, richly perfumed, perfect for cutting. Although their ancestry was sometimes echoed in cultivar names such as The Czar, these sweet violet hybrids were the foundation of a very English cult.

Meanwhile, the French had a cult of their own, also the result of people in high but faraway places. In the 16th century, violets ‘with flowers like roses’ had travelled the same route as tulips and Persian lilac, carried from Turkey to Italy. There, they were crossed with a local species, producing plants with glossy leaves, large double flowers and surpassing scent. When the Bourbons came to power in Naples in the 1730s, they took them to their hearts. They also took them north, to another of their domains-Parma.

After Napoleon’s conquests, Violettes de Parme began arriving in France. By the 1850s, they were being grown commercially in Toulouse. Nonetheless, they never lost their class. Commemorating empresses, princesses, dukes and counts, their cultivar names read like the Almanach de Gotha. These blooms were as close as any real Eliza Doolittle would ever come to a Ruritanian prince. To add to their mystique, nobody knew what went into a Parma violet. Save for the odd self-fertilised seedpod, they were usually sterile.

This led growers to speculate that they were hybrids between Viola odorata and V. suavis. But crossing these putative parents invariably failed to produce the real thing. Parma violets seemed to have sprung from some horticultural alchemy held secret by ancient families and lost in the Age of Revolution. Only in 2007 did botanists examine their DNA and discover that they all have just one wild ancestor-Viola alba, a species widespread in the Mediterranean and Near East.

A violet revival is emerging, with new cultivars in production, but among Parmas, I’d recommend Marie-Louise (amethyst with a ruby-flecked white centre), and Conte di Brazza (ivory, like a miniature gardenia). Among sweet violets, I favour King of Violets (double, azure splashed with white), Perle Rose (single, cerise), Pamela Zambra (single, large, Imperial purple), and Crépuscule (single, apricot washed with lavender). These and others just as irresistible can found marked (PVt) and (Vt) respectively beside their stockists in the RHS Plantfinder.