In the spring of 1846, Francis Parkman, a 23-year-old Harvard graduate, boarded a steamboat in St. Louis, bound westward for the Rocky Mountains. “The Missouri is constantly changing its course, wearing away its banks on one side, while it forms new ones on the other,” Parkman wrote of his first impressions on the river. “Its channel is continually shifting. Islands are formed, and then washed away, and while the old forests on one side are undermined and swept off, a young growth springs up from the new soil upon the other.” Parkman would, over the next four decades, become a leading historian of the American west, but even as a young man, he was an acute observer of the botanical landscape. At one point on his expedition, shortly after his team departed the Missouri River near present-day Kansas City, exchanging steam power for horses, Parkman recounted sprawling in the green prairie, surrounded by a profusion of blossoms, caught in a moment of revelry as he remembered gardens in Boston.

The whole story of how Parkman the Historian became Parkman the Horticulturist is sinuous. But in brief, in 1852, Parkman purchased three acres on the shore of Jamaica Pond—less than a mile from the yet-to-be-founded Arnold Arboretum—and there he began cultivating roses and Japanese plants and other horticultural curios. In 1866, he published a book on roses, and in 1871, he was appointed the first professor of horticulture at Harvard, an academic position based at the Bussey Institution, adjacent to property that would shortly become the Arboretum. In 1872, Parkman resigned from the position, owing to a combination of family tragedy and persistent health problems, and his neighbor and friend Charles Sprague Sargent was appointed in his stead. Sargent was simultaneously named curator of the newly established Arboretum, and the following year, he became the Arboretum’s first director—a position he would hold until his death in 1927. When Sargent published the third volume of his Silva of North America in 1890, he dedicated it to Parkman, noting that the historian’s “words have best painted the beauties of the American forest.”

It seems appropriate, given all of this, that a tree from Parkman—or rather a tree grown from seed Parkman provided—would greet visitors who enter the Arboretum near the Hunnewell Building: a massive cucumbertree (Magnolia acuminata, accession 15154*D). As the strange common name may imply, the tree—though an American species of magnolia—is not well-known for its flowers. This year, the flowers came and went in early June, and chances are, for many who walked on the sidewalk, beneath the tree’s elbow-like branches, the blossoms registered most clearly once the greenish cream tepals fell to the ground, where they were muddied into the concrete. The flowers, for those who notice, are interesting, even curious, but they are nothing like the showstopping pinks and whites of many Asian magnolia species—the kind of display that sends even Instagram skeptics into selfie-snapping frenzies. At this moment, however, on the brink of September, fruit on Parkman’s cucumbertree is abundant. The pink, finger-shaped knobs more closely resemble cornichons than modern pickling cucumbers, and some are distorted with strange bulbous protuberances, which will eventually erupt, revealing vivid orange seeds inside.

The Parkman cucumbertree stretches over the sidewalk, outside of the Arborway Gate.
The Parkman cucumbertree stretches over the sidewalk, outside of the Arborway Gate. Jonathan Damery

The Parkman tree, moreover, stands in a sort of founders’ grove at the Arboretum. As you walk towards the gate, a small, gangly tree (or perhaps I should call it a large shrub) hangs over the wall, with impeccable foliage—sleek green on one side, near white on the back. The bark is patched with lichen, and the fruits resemble those of the cucumbertree, although most are still white with immaturity. This summer-flowering tree—a sweetbay magnolia (Magnolia virgininia, accession 15163-1*B)—is a seedling from plants received from John James Dixwell, a banker who lived on a 10-acre property between Parkman and the Arboretum. One of the original sweetbays from Dixwell grows right beyond this one. Like Parkman, Dixwell was a passionate plantsman, who developed a private tree collection that Sargent, writing in 1923, would describe as “one of the most important and interesting in New England.”

Incidentally, Dixwell became a good friend of a whaling merchant and avocational horticulturist from New Bedford—a man named James Arnold. When Arnold died, Dixwell was one of three trustees for the estate who was involved with finding a home for the arboretum that would bear Arnold’s name. Several other plants around the Arnold Arboretum—including several cucumbertrees—trace their lineage back to Dixwell. Likewise, several other Parkman plants grow in the collection as well. Suitably, while neither Dixwell nor Parkman’s private gardens remain today, their plants continue to usher visitors into the Arboretum, welcoming them with flowers and fruit, year after year.