When I installed this collection on the edge of the larch wood a few years ago, I did so with nothing more than nostalgia in mind, and possibly the happy memory of eating blueberry slump in the New England Berkshires. That the plants (like me) were American natives passed through my mind, but it never occurred to me to make anything of it. And though I recognised that they all preferred acid soil conditions, that, too, seemed to be purely a matter of accident.
I now learn that what we've got here is at least the nucleus of a garden type that for more than 100 years, starting in the late 18th century, played a role of some importance in British horticulture and garden design. At the beginning, the American Garden was at least partly responsible for bringing home the blossoms so high-handedly banished by the great landscaper Capability Brown; in its later life it saw the vast and colourful development of rhododendron and azalea culture. By that time, of course, it was scarcely American at all, but a motley mixture of plants from all over the world, unified mainly by their hatred of chalk.
The earliest American Gardens were made to accommodate species coming in from the New World - kalmias, azaleas, rhododendrons, low ground covers such as wintergreen (Gaultheria procumbens), cassiopes and bog rosemary (Andromeda polifolia). All of them seemed to like peaty, boggy, acid earth; there has been speculation that the first explorers, travelling along river valleys, naturally came upon such plants there. Seeds and plants gathered by American naturalists such as John Bartram, working largely along the Eastern seaboard from New England to Georgia, had been flooding into England. So many American plants were available by the 1760s, in fact, that Sir William Chambers could speak derisively of "American weeds" when attacking the work of Capability Brown.
It was Brown's successor Humphry Repton, however, who made a real virtue out of the "weeds". Repton realised that many of his clients enjoyed flowers, provided they could be brought back into the landscape scene in an interesting fashion. That the term "American" still had overtones of the savage or wild did no harm in those days around the turn of the century when the taste for the picturesque ran strong. So where Brown had depended mainly upon sweeping expanses of lawn studded with trees for his effects, Repton added excitement in other ways. These included separate smaller gardens that could be enjoyed independently, and many of them - as at Woburn Abbey, Bulstrode, and Ashridge - were American Gardens.
As the fashion and the availability of New World plants spread, other designers followed suit. The nurseryman Lewis Kennedy of Hammersmith built American Gardens at several estates in the Home Counties. At Fonthill Abbey, his vast and killingly expensive estate in Wiltshire, the eccentric William Beckford made what he called an American Plantation above the lake. It featured a large collection of flowering American trees and shrubs such as magnolias, robinias, liquidambars, azaleas and rhododendrons.
Though at first they were not very interesting - mostly unexciting shades of pink or mauve - rhododendrons were destined to become the stars and the nemesis of the American Garden. Peter Collinson had introduced the first American variety in 1736, the Carolina rosebay (R maximum), planting it in his garden in Peckham, and more followed. Somewhere around the 1760s or 1770s R ponticum - not from America, but from the Black Sea coast of Turkey - opened its gross purple blooms in England for the first time. R catawbiense (actually an American ponticum) arrived in 1809, not long after a yellow-flowered variety, R caucasicum from (obviously) the Caucasus. The American Garden was becoming international, a process encouraged by the discovery that crossbreeding among rhododendron and azalea species was relatively easy, and could produce spectacular results.
In Belgium, growers crossed American azaleas (especially the Pinxter flower, R nudiflorum, whose pink blossoms glowing on leafless stemsin a bare early spring Appalachian wood are such a poignant sight) to create a wide variety of so-called "Ghent" azaleas. Then, in 1820, crossbreeding of the rhododendrons proper took off in earnest with the introduction of the first in a long series of imports from East Asia, R arboreum, with its massive blood-red blooms. Soon plant breeders were successfully tinkering with the whole range of characteristics - size and form of bloom, fragrance, flowering schedule, hardiness, and above all colour. The Rhododendron Era was at hand.
It rather overwhelmed the more unassuming concept of the American Garden, even though as late as 1843 J C Loudon was proposing an American Garden as part of his plan for Coleshill in Berkshire. But it has to be admitted that Loudon, for all his fame, was not an innovator. What passed for an American Garden during Victoria's reign tended to involve almost anything suited to acid soil - lilies, various conifers, heathers - no matter where it came from. Gradually the term itself fell into disuse.
Rhododendrons and azaleas, meanwhile, found their way out into extensive and often garish plantings, encouraged by the import of still more exotic varieties from the Himalayas, China, Tibet, Japan and the rugged no-man's- land of Upper Burma. A modest mountain laurel or bearberry, or even a perfumed sheet of trailing arbutus, was scarcely a match for a valley full of Lionel de Rothschild's brilliant Exbury azaleas, or a copse aglow with one of George Forrest's rhododendrons from Yunnan. You can see what I mean by visiting, for example, the long deep combe lying behind Lydney Park in Gloucestershire on a day in late May, when the hybrid rhododendrons are in all their blinding glory.
Perhaps it is misplaced patriotism, but I rather regret this development. It would be nice to bring back the American Garden, at least in a small way, and I'd do it myself if I could figure out some way to acidify our good red Monmouthshire clay. We can think of a number of plants that would fit in nicely without demanding acid. I don't insist on rhododendrons anyway, and for that matter already have a large clump of R ponticum, which came with the house.
We should note in this connection that rhododendron fanciers - at least the 18th-century ones - have something to answer for. That ponticum, so hopefully introduced 250 years ago, has now become a simple British weed. Its leathery leaves and purple blossoms are smothering hundreds of acres of irreplaceable heather moorland from Surrey to Snowdonia. You can hardly kill it; most animals refuse to eat it (reportedly, only llamas are willing). The National Trust has gone so far as to institute a ponticum-destruction programme. My ponticum has not smothered anything yet, but I'm keeping an eye on it.
Charles Elliott writes for 'Horticulture' in the US. His articles will be published here on 25 April in 'The Transplanted Gardener' (Viking, pounds 16)
Anna Pavord is on holiday