Deep purple: There are hellebores - and then there are Rodney Davey's hellebores

The first plants I ever put in the ground at our new garden were hellebores. Not any old hellebores. Rodney's hellebores. February can be a grim month and for the past 15 years, when grimness threatened to overwhelm, I've jumped into the car and driven through the lanes to Rodney Davey and Lynda Windsor's nursery in Tytherleigh. The scene was always the same. That was part of its charm. Rodney, in his apron, would be standing at a wooden bench in his polytunnel, potting up baby hellebores. Running down the centre of the tunnel would be trestles full of the most astoundingly beautiful flowering hellebores that anyone has ever raised.

Quietly, slowly, you could move down the length of this 'For Sale' selection, gazing into the faces of speckled flowers, anemone-centred flowers (my favourites), double flowers with petals curved in like claws, flowers the colour of pale jade, flowers of a purple so deep and lustrous they seemed almost black. Rodney will have grown every single one of these plants from his own seed, selecting, rejecting (mostly rejecting) seedlings to amass a collection that, each year, showed some new trait that he will have had in mind. For quality, nothing can touch his plants. He's the most uncompromising, rigorous plantsman I've ever met.

Then, a few years ago, something extraordinary happened. I turned up in February as usual. Rodney was potting up seedlings as usual. But standing on its own, close to his workbench, was an unusual hellebore with outstanding marbled foliage and flowers of a deep, rich purple-red. "Wow," I said, never having seen anything like it before. Until now, if you wanted hellebores with interesting foliage, you'd turn to x ericsmithii types – 'Winter Moonbeam' for instance. But the flowers of x ericsmithii hellebores are always pale greeny-white colours. This combination of a deep-red flower with beautiful marbled foliage (on young leaves the marbling is pink, turning to cream as they age) was something entirely new.

I peered into the flowers, noting the size, the depth of colour, the symmetrical perfection of the creamy boss of stamens in the centre. Gently, I fingered the leaves with their beautiful markings. "Wow," I said again. "It's just as well you like it," replied Rodney, who generally doesn't say much. "Because I thought I'd name it after you." Which is why, when I visited the nursery again this week, Lynda Windsor had just spent a tedious morning writing several hundred labels for Helleborus (Rodney Davey Marbled Group) 'Anna's Red'.

It took Rodney 12 years to achieve his goal of raising a red-flowered hellebore with marbled leaves. First of all he had to create the mother plant, painstakingly transferring pollen from one hellebore to another in the hope that at least a few of the seedlings raised from the cross would carry the characteristics he was looking for. When finally he was satisfied with the mother he had created, he started on the next round of crosses, using the pollen from several different hellebores. For years he sowed the seeds that resulted from this second round of crosses, putting the best to the best, but in each batch of a thousand seedlings, he rarely kept more than two to grow on.

Sometimes, only a few seeds would germinate. The dream hellebore that Rodney was pursuing seemed to be locked up inside seedcases with particularly hard helmets that refused to release the germ inside. Rodney tried to soften the seeds by spraying them with water, but they could not be persuaded to open. They were too delicate to cut or force open by hand. For many propagators this would have been impossibly frustrating, but Rodney likes a challenge.

Finally, after years of work, he began to recognise characteristics in some of his hard-fought-for seedlings that suggested he was on the right track. Even before young plants flowered, he guessed from the deep purple flush on their stems that their flowers were likely to be equally lustrous. After several more years' laborious work, fighting the seeds' obstinate desire to stay locked up, he finally selected the seedling that has become 'Anna's Red'. But to build up enough plants to sell, he had constantly to recreate the cross he'd made. It took several more years to build up a stock of two hundred plants in pots.

At which stage, word trickled out, through fine nurserymen such as John Massey, that Rodney had created something that nobody had managed before in the world of hellebores. Massey introduced Lynda and Rodney to a Dutchman, Bart Noordhuis, who persuaded them to let him micro-propagate the plants. Even this, at the beginning, was not easy. Plantlets would develop in the gel of the test tube, but were reluctant to move on to the next stage and root into proper compost.

By the autumn of 2010, micropropagating techniques had changed and finally, Noordhuis reported that he'd got 100,000 seedlings of Rodney's hellebore growing on nicely for the European market. They'll be widely available next year. Meanwhile, a few hundred of the little plants came back home to the Tytherleigh nursery and are going on sale for the first time this month. His success will not make him a millionaire (he'll get just 20 euro cents for each plant sold) but making money has never been the raison-d'etre of the nursery.

So why do they do it, you wonder? The hours are long. Losses can be sudden and unforeseen. And if you specialise in hellebores you have to make most of your year's income in the three months of spring.

Because they love plants, said Lynda. They saw too many weedy, small specimens, indifferently grown, which turned out, when they flowered, not to be what they said they were. They thought they could do better. Over the past 15 years, I've bought some wonderful things from them: the elegant fern Polystichum setiferum 'Bevis', autumn-flowering Cimicifuga simplex, an enchanting little dicentra, D. cucullaria, with blue-green leaves and white flowers, the almost impossible to propagate blue Pasque flower called 'Budapest'. Almost impossible is what Rodney likes best.

Rodney grows the plants. Lynda organises the rest. What happens when you go away? "Oh, I don't go away," said Rodney, quickly, with a shocked look on his face. "Rodney can't go over the Devon border," explained Lynda. Rodney smiles quietly into his beard. "He'd get jet lag if he went a hundred miles from here." So he doesn't. He has no driving licence. No passport. And no desire for either.

The nursery has been a full-time business since 1992. Of course, to grow any plant well, you need to pay attention to the detail. "Not spreading yourself too thin," is the way Rodney puts it. He likes time to water properly. There's no wholesale overhead spraying here. Each plant gets what he thinks it needs. Many of the hellebores grow in extra-deep, two-litre pots because he has found they then establish better root systems.

I've had 'Anna's Red' in the garden for three years now. Fortunately, it's a lusty plant and grows with great vigour. I'm so glad. It would be very weird, dying as it were by proxy.

'Anna's Red' (£20) is available in limited numbers from RD Plants, Homelea Farm, A358 Chard Rd, Tytherleigh, nr Axminster, Devon, 01460 220206. The nursery is open daily (10am-4pm) until the end of May. There is no mail order. Flowering specimens of 'Anna's Red' will also be on sale at the Hellebore Weekend (25-26 Feb), being held at Great Dixter, Northiam, Rye, E Sussex TN31 6PH. For more details call 01797 252878 or visit greatdixter.co.uk