East End. With that in mind I’ve long wanted to visit the Polly Hill Arboretum in North Tisbury, a treasure trove of azaleas and rhododendrons, magnolias, dogwoods, and, most important, stewartias. If they flourish on Martha’s Vineyard, they should do equally well here. The trick is to find sources for those that capture our fancy.
Polly Hill, for whom the arboretum is named, was an amazing woman, and gardeners around the world are benefiting from her patience, discerning eye, and longevity. She didn’t plant her first seed until she was 50 in 1958. Yes, she grew almost everything from seed. There was no greenhouse; seeds went directly into the ground! Many of the plants date back to the late ’50s and early ’60s, enabling visitors today to enjoy mature, 50-year-old trees and shrubs.
Mostly Mrs. Hill obtained her seed from a friend in Japan and from collectors and arboretums in the United States. Fortunately and like many of the best, most adventuresome gardeners, she lived a long and productive life, to 100. She observed her plants, waiting decades in some cases for them to flower, and then selecting, naming, and distributing the best. At the rear of the arboretum is an area called Polly’s Play Pen where many of her selections were transplanted and can be seen today.
Stewartias, which bloom in late June and into July, are among my favorite trees, and for years I’ve dreamed of making a pilgrimage to see Polly Hill’s selections in flower. On a recent Sunday morning the stars were in alignment: The air was clear, a friend with a little Cessna was willing and available, and an hour after leaving East Hampton we landed light as a butterfly on the Vineyard. The arboretum is less than a 10-minute taxi ride from the airport.
Greeting us, appropriately, at the entrance to the arboretum was a grove of mountain stewartia, S. monodelpha, the ground covered with their fluttery, fallen, small white flowers. This is the species with glowing mahogany or bronze bark, and the best, grown from seed from the giants at the Barnes Foundation in Merion, Pa., have wide outspread branches running parallel to the ground.
The weight from the masses of buds and flowers on mountain stewartia can twist the outermost branches, so I was interested to see how they are pruned, and, yes, one of the first things I did on returning home was to prune my tree, as far up as I could reach. It pays to clean up the interior of the trees to reveal the shape of the branches and the color of the bark through the foliage.
One of the most photographed of Polly Hill’s Stewartia pseudocamellias, the most popular species, is the selection she named Mint Frills. Positioned at the front of another grove of stewartias, it was in full flower, a perfect photo op. Most stewartia petals are pure white, but this cultivar has a wash of soft lemon-lime on the petals. Farther along in the grove is Ballet, a very robust tree with flowers larger than most.
The bark of S. pseudocamellia exfoliates, leaving buff, mauve, and brown patches that are particularly attractive and welcome during the winter. We were astonished to see one tree, planted on its own by an old farm outbuilding, with white, black, and gray bark, looking for all intents and purposes like military camouflage.
The sign of a great garden, for me, is finding surprises, whether they be design ideas, plant combinations, or just plants themselves. Little did I suspect that in addition to the famed North Tisbury hybrid azaleas that Polly Hill introduced, she was also interested in deciduous native azaleas. Now that we have a deer fence at the Mimi Meehan Native Plant Garden here in East Hampton, I’ve been researching relatively low-growing deciduous azaleas that flower in July, when the garden gets many visitors.
There they were, planted in groups of three in partial shade, with fiery orange flowers demanding attention. Originally the species was bakeri, but now it is called Rhododendron cumberlandense. Native azaleas can be difficult to propagate, but by next summer there will certainly be some R. cumberlandense growing in our native plant garden.
A visit to the arboretum in the spring should definitely be on the agenda for lovers of rhododendrons. Mrs. Hill clearly was more interested in the foliage than the flowers, and again she grew most of her species rhodies from seed, although there is a large selection of hybrids as well. There are many R. makinoi, which have long, narrow, dark green leaves, and another species, R. degronianum, both of which have soft fawn-colored indumentum underneath the leaves.
Japanese dogwoods were among Mrs. Hill’s favorite trees and she grew many from seed from a particular tree in Pennsylvania, naming the most interesting. We’ve been looking for a very special summer-flowering tree for a public space in East Hampton, and we found it in a place of honor at the arboretum — not a Polly Hill introduction, but recommended as one of the best: Summer Stars. Most Japanese dogwoods bloom in June, but Summer Stars was at its peak in mid-July, perfect timing for the high season here.
The Polly Hill Arboretum has top horticulturists on its staff who are continuing Mrs. Hill’s mission of growing new woody plants worthy of introduction. In the June issue of the Royal Horticulture Society’s journal The Plantsman is a tantalizing article on enkianthus, co-written by the arboretum’s Tom Clarke, the collections and grounds manager, and Eric Hsu, a research associate. I’m looking forward to returning to the arboretum to see the enkianthus when they have a little age on them.
Actually, I’d love to return for a month or six weeks as an intern to observe the cycle of flowering from these magnificent collections.
Stewartias are notoriously difficult to propagate, so availability of the Polly Hill selections is limited. Broken Arrow Nursery in Connecticut and Greer Gardens in Oregon have perhaps the best selections. Other sources of stewartias are Fairweather Gardens and Rare Find in New Jersey and Forestfarm in Oregon.
The Horticultural Alliance of the Hamptons is planning a trip to the Polly Hill Arboretum in September. Go . . . and you will surely want to return.