We were in Truro market when my companion opined that it was a man thing, this quest for the perfect pork pie. She left me to it with that mixture of scorn and pity usually reserved for addicts to stronger fare. In this Cornish cornucopia, my luck, I felt, was in. Before long, I’d found a prince among pies. Then, as I stood busily destroying the evidence of my private vice, my gaze fell upon an even greater prize. It was a plant named Cannomois virgata, a South African native that made its Chelsea Flower Show debut some years ago to loud acclaim.

Since then, it has proved agonisingly hard to obtain. Suddenly, there it was betwixt the saffron cakes and clotted cream, offered as casually as any other garden plant and cheaper than a post-Yule poinsettia. ‘Only in Cornwall,’ I mused, handing my crust to an importunate seagull and groping for a tenner.

Although its name in Afrikaans is bergbamboes, ‘mountain bamboo’, Cannomois virgata is not a grass but a restio, a member of the Restionaceae, a family of stately Southern Hemisphere perennials. Their grace and usefulness are in inverse proportion to the slow progress they have made in our gardens since they began to arrive here at about the turn of the millennium. This is for three reasons.

First, restios are believed to be tender. They are proving hardy, however, in sheltered sites in much of the country from Oxford southwards, and they flourish in cities. One celebrated garden designer, for example, has used another restio, the giant rush-like Chondropetalum tectorum, solo in zinc containers around a Minimalist building in central London in the coolest passage of modern planting I know. Second, restios are peculiarly demanding about soil.

They need an acid-to-neutral, moist, free draining and, above all, low- fertility medium: to feed them is literally to spoil them rotten. A tub or a generous planting hole filled with equal parts peat, ericaceous compost, alpine grit and horticultural sand will do. Leave the Growmore in the shed.

The third reason for the staggered debut of these staggering beauties is that many of them are propagated by seed whose germination is triggered by exposure to smoke. This evolutionary adaptation prevents them from competing with each other: not until a bushfire has created more territory will the seeds sprout to replace their incinerated parent plants. Would be restio producers have only recently worked out how to replicate this essential kippering to meet commercial demand.

One of the few growers to have cracked the dormancy of Canno-mois virgata is Chris Osborne of Churchtown Nurseries, Gulval, Cornwall (01736 362626). It was his mother, Fay, who brought my years of waiting to an end by selling me a bonny young specimen in Truro market. The wait was worth it.

The plant stands about 3ft tall, its canes whorled with ascending masses of filamentous branches picture a clump of upturned besoms. At its base, next season’s growth is already apparent in the form of fat buds that resemble brick-red bamboo shoots. Their ruddy sheaths persist as the new canes extend, in brilliant contrast with the soft and billowing pea-green foliage. There are no leaves as such and the flowers when, or if, they appear will be small, brown and chaffy.

The plant is a marvel of airy elegance, both radically simple and infinitesimally complex. In its native Cape, Cannomois virgata soon reaches a height of 16ft, hence another of its verna-cular names, Olifantsriet or ‘elephant’s reed’. In maturity, it has not only the stature and presence of the very best bamboos, but also a finesse unsurpassed by any other plant. That said, other restios come close the feathery Elegia capensis, for example, or filigree Rhodocoma gigantea, both more widely available.

The next and perhaps ultimate phase of our new-century love of grass-like plants, the Restionaceae is a family that has the potential to transform our gardens. Not that my Truro treasure will transform my patch here in Oxford. For safety’s sake, I left it in Cornwall, at Carbis Bay, planted in my parents’ garden, a landscape of granite monoliths and subtropical luxuriance where it seemed instantly at home. We will not be apart for long. Of late, the City of Dreaming Spires has become the stuff of nightmares. By the next time I write, my entire garden will have migrated south with me to the Duchy of plant pioneers and the perfect pork pie.