Rheum nobile is a curiously majestic plant that you're not likely to find for sale in many nurseries or seed catalogues. When it is some years old it sends up a five-foot nose-cone covered from broad base to pointed tip with great, floppy bracts - creamy at first, and withering to a rich, tobacco brown. After setting thousands of seeds in the sheltered, private space under its bracts - and thus ensuring the continuation of its noble lineage - the exhausted plant dies.
I've never seen it flower, but I have seen it die - at my own hands. For months, I had proudly parented an infant plant grown by a friend from seed he collected at 4,200 metres in Tibet (where, in its native, mist-cloaked habitat, colonies of this lunar-landscape plant have apparently been mistaken for parties of eerily-quiet soldiers).
Anyway, one week my shiny baby was all full of plump promise, and the next its dark glossy leaves had lost their lustre and lain down in the pot, very dead. As is the case with most herbaceous deaths, grieving was swift and pragmatic. That is, until recently, when I picked up a wonderful new book, The Explorer's Garden, by American nurseryman and plant hunter Dan Hinkley. There, photographed in eastern Nepal, were grown-up versions of the infant I had slaughtered: their conical rockets of translucent bracts blasting a pang straight through my erstwhile-hardened heart. But comfort was there also: Hinkley points out that Rheum nobile "may be more ideally suited to extremely cool and moist conditions such as Scotland or maritime Alaska" rather than his own Pacific north-west climate in Washington state, which is not unlike ours in this country.
The noble Tibetan rheum, as any gardener knows, is just a fancy rhubarb, and one of a "wealth of species and hybrids that convey polished effect to the garden rather than simple harvest to the kitchen". Dan Hinkley devotes an entire chapter to them. By the time you're finished reading it you want to grow them all.
Hinkley has chased rheums in Nepal and China. He's gone after gunnera in Chile (while noting that Gunnera tinctoria has escaped in parts of Ireland and "made a rather robust nuisance of itself"). He has hunted down wild Scopolia (a beautiful woodlander with Art Nouveau lampshades for flowers) in Korea. In that country he has also observed Rodgersia, which he's seen as well in its native Japan and China. He's studied this genus in gardens in various corners of the globe, and the best form he has obtained of R. pinnata, known as `Elegans', "came from the superb garden of Helen Dillon in Ireland".
In the 28 chapters of this book, each one devoted to a particular genus or related genera, Hinkley rambles from country to country in search of his favourite plants roaming free in their natural habitats. Every discovery is not just a thrill, but also a clue as how best to grow the plant in captivity. At the end of each chapter he gives notes on cultivation, propagation and hardiness. All the plants, by the way, should grow in our mild Irish climate - which in the often-quoted American "zone system" (based on minimum winter temperature) approximately encompasses zones seven to nine. Some of the plants are new to me: I've never heard of Pinellia, a relation of the jack-in-the-pulpit Arisaema clan, nor have I heard of the "comely composites" with beautiful foliage, Syneilesis and Ainsliaea, from South Korea.
Hinkley's choice is entirely subjective, embracing many plants that are not particularly well-known or documented. He leaves out things like clematis and primula that have been exhaustively covered elsewhere. His chapter on Corydalis (the name comes from the Greek for "crested lark") is masterful, and will be of interest to all those gardeners who fell for the highly chic - and beautiful - blue versions: `Pere David', `China Blue' and `Purple Leaf'.
He discusses the rare Saruma henryi, an interesting yellow-flowered plant, first collected by Irishman Augustine Henry during the 19th century, but introduced into cultivation just a decade ago. It is causing quite a stir across the Atlantic among plant sophisticates (and its name, incidentally, is an anagram of the closely related Asarum genus).
Hinkley is full of interesting snippets: that in China Epimedium acuminatum is rampageously collected as a cure for male impotence; that in Japan certain varieties of Hepatica "are priced in the range of several hundreds to several thousands of US dollars"; that the sky-blue Chatham Island forget-me-not (Myosotidium hortensia) is reputed to germinate better if the pots are watered once in sea water.
This is a book that is filled to the brim with an elite gathering of plants: few are brash and overly noisy, many are charmingly understated and some are downright esoteric. But I bet my bottom dollar that all are destined to become, if they're not already, coveted plants for discerning gardeners worldwide. Hinkley, to his credit, is acutely aware of the gullibility of the plant-hungry gardener and tells how: "I was at one time duped into purchasing a curious clone known as Cardamine pratensis `Improperly Dressed'. With foliage identical to that of the common cress . . . this plant bore flowers that lacked petals as well as any obvious reason to cultivate it."
The Explorer's Garden by Daniel J. Hinkley is published by Timber Press (£29.99 in UK) and can be ordered from good bookshops or over the Internet from www.timberpress.com, where you will pay £8 sterling in postage
Diary date: Tomorrow, 2-4 p.m. at Our Lady of Dolours Parish Hall (under the Pyramid Church), Glasnevin, the Irish Garden Plant Society's annual Dublin sale. Rare and unusual plants including Irish cultivars, indoor plants, interesting roses and a limited number of Tibetan species grown from wild-collected seed