A cart ride through Boston’s tree-filled treasure

When you plant in the garden, how far ahead do you look? Three years, maybe 10? I have just spent time in a superb arboretum whose horizon extends for a 1,000 years, renewable, like its lease, for another 1,000. Try thinking of 3872, 2,000 years after the arboretum’s beginning, when you next dig a hole for a tree.

The Arnold Arboretum in Boston is unmissable, one of the world’s finest. Over the decades its curators have crossed, bred and selected new shrubs for gardeners, many of which I have enjoyed. I often recommend the white Magnolia x loebneri Merrill, which flowers freely at an early age: Arnold Arboretum’s former director ED Merrill selected it. Forsythias are mainstays of spring but some of the best derive from the Arnold Arboretum too. “Beatrix Farrand” commemorates the great landscape gardener who studied in the garden. “Arnold Giant” is less familiar but it is an excellent forsythia whose yellow flowers are bigger and paler and especially pretty when branches of it are picked in bud and allowed to open indoors. Before it flowers we can enjoy a Boston-bred witch hazel too, Hamamelis x intermedia “Arnold Promise” with bright yellow flowers and especially curly petals.

Despite growing these Arnold introductions, I had never seen the arboretum itself. So the director, Ned Friedman, offered to initiate me into its highlights, even on a Sunday in August. He is a biology professor at Harvard University with which the collection has been linked since inception. “It’s Boston’s dirt and Harvard’s trees,” he explained to me: the arboretum now extends over some 280 acres. Would I have to walk it all with a professor? “I am the only Harvard professor,” he reassured me, “whose job comes with a golf cart.” One of my ideas of heaven is to glide in a golf cart through large gardens, admiring the surrounding grass and braking to inspect the sights of the day.

Since its inauguration in 1872, the arboretum has owed a special debt to two guiding geniuses. Its first director was Charles Sargent, who ran it for 55 years. In 1892, he visited Japan and east Asia, confirming the arboretum as a haven for plants from the east. Among gardeners his name lives on in a famous malus and a prunus but it is for this eastward turn that he deserves special thanks. The arboretum has a marvellous range of mature shrubs and trees from the east, many of which are invaluable for gardeners. One of Sargent’s most valuable sources was the great collector EH Wilson but the arboretum still maintains close links with Chinese, Japanese and Korean botanists, raising and protecting beauties from seeds collected in the wild.

I knew about Sargent but not about his inspired choice of landscaper. In 1882, he agreed that the new arboretum should be laid out by none other than Frederick Law Olmsted, the landscaping maestro of New York’s Central Park. An authoritative study of Olmsted’s North American landscapes appeared last year with the support of the Cultural Landscape Foundation (Experiencing Olmsted by Charles Birnbaum and others; Timber Press, $50), but it gives only two passing mentions to the arboretum. It has missed a major point. Floating through it in a golf cart, I agreed with Friedman that the arboretum’s plan of curving walkways, bridges, ponds and slopes is Olmsted’s crowning masterpiece.

In 1713, in his fine poem about Windsor Forest, Alexander Pope admired how “interspers’d in Lawns and opening Glades/Thin trees arise that shun each others’ Shades”. Throughout the arboretum they indeed arise but they are setting off serpentine lines that Olmsted’s eye initiated. When he drew and re-drew his master plan, the trees to be planted were thin indeed. He would never see their mature thickness but, being a genius, he could envisage them. Olmsted never knew about golf carts, either, but his broad pathways and looping plan through the garden are ideally suited to their movement. Turns and bends maintain an inviting sense of discovery while the grass and trees blend into many more than 50 shades of green.

The arboretum contains about 16,000 trees but it never stands still. “One in, one out,” reflects the disconsolate Rick in that matchless scene in the film Casablanca, mistaking his lost love Ilsa’s predicament. “Four hundred in, 400 out,” Friedman mused to me as we braked beside the arboretum’s wonderful collection of pines. In most years, about 400 trees die or fall, often uprooted by turbulent winters. Replanting is meticulous from the arboretum’s nursery stocks, backed by its skill in propagation. “Whatever we are sent, we eventually crack,” Friedman assured me. The seed bank is not lying idle.

The trees are grouped in general species, pines, limes, acers, including the rare big-leaved maple, and oaks, including Sargent’s oak, a cross between an English oak and a chestnut oak that happened to occur on Sargent’s own farm. The beeches even include a parasol beech, a low-growing rarity with twisted branches that came as a gift from Kew in 1888. When I asked Friedman for his impossible top three picks, he chose a ginkgo, subject of his doctorate, a flowering Franklinia, which was found in the American wild in 1776 and is now only known in cultivation, and the amazingly varied bark on the rare lacebark pine from China. Of course, he could have picked another 100.

We bowled along among trees that have gained from his recent study, whether the big-leaved Magnolia macrophylla, whose sticky parts he realised to be killers of visiting bees, to cones on one of the pine trees that he observed to be hermaphroditic, the first non-binary pinus. There is so much more to understand, he kept remarking, not least why bark differs. The bark of the lacebark pine varies in colour with its aspect. The arboretum has huge specimens of Acer griseum, the lovely maple from China whose tattered bark peels like skin from its trunk.

A more sheltered bank leads to the well-named Explorers Garden, a section keen gardeners must not miss. Here some of the loveliest finds from the wild survive the winters, including a big silk tree, Albizia julibrissin, with pink-white flowers like powder puffs. Wilson found it growing in a hotel courtyard in Korea in 1918 and sent seed back, not expecting it to survive many winters. The first tree is still growing.

This month I will enjoy little white and blue-centred flowers on my heptacodium, rediscovered in my lifetime in China. However, it was already known from a specimen found by Wilson in 1907 and was classified botanically in 1916. It was introduced into the arboretum in 1980, where the trees are far bigger than I ever imagine mine to become and their leaves are broader and finer. What a wonderful surprise.

The arboretum is run with a core staff of 16 gardeners, devoted to the place. A yearly budget of $17mn covers its maintenance, archiving and research, about four-fifths of which is met by external institutions, especially Harvard. Donations and carefully limited events meet the rest. As a result, the arboretum remains free for visitors, a prize of the first order. Olmsted was explicit that each individual has a right to space, a principle embedded in the arboretum since its foundation. In 2020, during the lockdowns, Friedman was adamant that social distancing could be followed: 3.5mn visitors benefited. Lucky Bostonians, with such a loved treasure at their feet.

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