Some of the most familiar plants in the garden originated in Southeast Asia. Azaleas, rhododendrons, hostas, wisterias, lilies, daylilies, camellias, and viburnums, to name a few, have made us feel so much at home that our world, ironically, would feel alien without them.
Many of these plants have cousins native to North America, but it is the trove of Asian plants that directly, or indirectly through hybridizing, have come to define our gardens: the showy flowering evergreen azaleas of April, the saucer magnolias of March, and the summer blossoms of the hydrangea and crape myrtle.
Japan, Korea, Taiwan and the southern provinces of China west to Tibet, as well as Bhutan and Nepal, drew 19th- and early-20th-century plant collectors from the West who found in these regions a horticultural Shangri-La. The ice age glaciers that erased much of the flora of Europe and North America were blocked by the Himalayas and other mountain ranges. The result?
"The number of plant species within the boundaries of China is 10 times the plant species we have in North America," says Dan Hinkley, whose five-acre garden overlooking Puget Sound in Washington state has, it is fair to say, its share of these treasures.
Mr. Hinkley has spent two decades retracing the steps of such legendary plant explorers as Robert Fortune (1812-80), Jean Marie Delavay (1834-95), Armand David (1826-1900), Ernest "Chinese" Wilson (1876-1930), and George Forrest (1873-1932).
Theirs may have been the golden age of Asian plant collection, but the spirit of the period is very much alive among a handful of 21st-century collectors such as Hinkley. His work may take decades more to flower in Western gardens, but the tradition, the impulse to brighten our lives with fantastic Asian plants, persists.
Hinkley's forerunners stayed for years in Asia, often assembling armies of local inhabitants in their quest. They faced perils and privations Hinkley hasn't, including disease and physical threat, but they had certain advantages. They could evaluate plants in spring or summer bloom. Hinkley typically goes for 12-week stints in two or three countries, but during the seed-ripening months, September through December. He only sees how they bloom back in his garden, sometimes years later.
There is a cousin of the climbing hydrangea with the unfortunate name of Schizophragma hydrangeoides. It is a magnificent leafy vine that, in my garden, took about seven years to bloom. In 1999, Hinkley took the seed of a close relative named Schizophragma integrifolium variety fauriei, whose blooms are twice the size but only now, this month, are fully unfurling for Hinkley for the first time. Wilson described this Taiwanese plant as "the most beautiful of the deciduous flowering vines from Asia," Hinkley says. "It has enormous impact."
Then Hinkley collected the seed of a mystery tree in central Japan, and it finally flowered to reveal itself as something called Pterostyrax corymbosa, a fairly ornamental tree, but if it were a fish, you might throw it back. "In some ways it was a much more exciting plant when you didn't know what it was for all those years," he says. "It's like an unwrapped Christmas gift, and then you open it and it's knitted mittens."
A decade ago, Hinkley wrote a book titled "The Explorer's Garden: Rare and Unusual Perennials," which describes the novel herbaceous plants he collected in his travels. A month ago, he published a sequel, "The Explorer's Garden: Shrubs and Vines From the Four Corners of the World" (Timber Press). As the subtitle suggests, it also includes woody plants from other countries, namely India, Australia, New Zealand, Chile, Costa Rica, and South Africa.
His finds in beguiling Southeast Asia, including northern Vietnam, represent a majority of the plants featured in the new book. Vietnam, he says, "is fascinating and one of the most unexplored areas botanically for plants appropriate for (parts of) North America," including the stretch from coastal New York to Florida. Many of the plants are tropical or subtropical but are winter hardy in the mid-Atlantic because they grow at high elevations.
Many of the plants that have captivated Hinkley are not entirely strange, being different species of more-familiar garden plants. There is a fascinating large shrub from Japan named glorybower or Clerodendrum trichotomum, valued for its bizarre late-season flowers, which consist of scented white blossoms that ripen to a purple fruit wrapped in brilliant red calyxes.
In his new book, Hinkley introduces us to another species, Clerodendrum fragrans, which has particularly handsome flower clusters, red in bud and opening pink. The shrub has a tendency to wander through suckering. "It is probably best to recommend it only for more natural landscapes or gardens that are soon to be put on the market," he writes.
Not every plant in the wild is a good candidate for the garden; quite the contrary. "Novelty is one of the least important things to look at when you're bringing plants into cultivation," he says. Hinkley, founder and former owner of Heronswood Nursery, is looking for plants that will show and behave well in the garden.
Sometimes, though, it's not that easy. "A whole lot of times," he says, "plants don't sing as loudly in the wild as under cultivation." He is thinking of a maple from Korea called Acer tegmentosum, which might be stressed and crowded in the wild but in the garden develops into a handsome tree with green bark striped white.
Hinkley sees his role as not only bringing a wider plant palette to North American gardeners, but also increasing the genetic diversity of ornamental plants. Clones of a hornbeam species from Sichuan named Carpinus fangiana don't set seed here because they lack a mate for cross-pollination. "I was able to collect 30 additional seeds this past autumn, and ultimately with more plants in cultivation it will be able to set seed," he says.
In 1996, he collected seed of a clematis named Clematis repens, which Wilson had collected in 1903 but which fell by the horticultural wayside. "Things are lost," Hinkley says. "Just because they have been in cultivation in the past doesn't mean they're still there."
"We'll see a lot of these plants used in breeding programs," says Nicholas Staddon, director of new plant introduction for Monrovia, a major wholesale grower based in Azusa, Calif. "There's a current, though, that possibly the best is yet to come out of China."
Monrovia has partnered with Hinkley to produce a series of his plant selections under Hinkley's name. The nursery launched seven plants this year, distributed mostly in the Pacific Northwest, but plans a nationwide release of additional plants in the spring.
One is an evergreen shrub named Disporum Green Giant that, when cut back in winter, forces new spring growth that is purple with white flowers. Another is a low ground cover named Beesia deltophylla, whose heart-shaped leaves emerge green and then turn blue before sending up little spikes of white flowers.
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