By Hannah Nelson
Washingtonians have a complicated relationship with the ginkgo tree.
The day I discovered the ginkgo outside my apartment was one of those distinctly DC beautiful days: the trees were that fresh green that comes at the end of spring and stays for early summer, the sky so blue you’d think it was cloudless, too.
The tree in question is on the grounds of the National Cathedral, in a pocket of grass that used to be my spot for fair-weather reading. Until this year, I’d never noticed it. Perhaps it was the direction from which I spotted it, coming to it another way, but this year, I felt myself drawn to it, at the whim of the natural—one might say spiritual—powers of this tree.
Up close, I reached up and traced my thumb over the uneven edges of its distinctive fans, half-wondering if there was some genetic pattern to them invisible to human eyes. The leaves called me to hold them and I did, a single leaf between my thumb and index finger. It was like the soft cover of a Moleskine notebook, only thick and indented with lines as I imagine dinosaur skin might have been.
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Ginkgo are “living fossils” and the only one of their species. Of the five groups of seed plants—simply, angiosperms (flowering plants), conifers (cone-bearing trees), cycads (tropical plants), gnetophyta (woody plants), and ginkgo—it is the only one that consists of a single species (by comparison, there are about 350 million species of flowering plants).
Even more remarkable is that ginkgo trees don’t visibly age and can live for hundreds to thousands of years. In a study published earlier this year, researchers compared gene expression in leaves and the cambium, a thin layer of stem cells between the heartwood and bark that differentiate to help the tree to grow. Although genes associated with cell division, cell expansion, and differentiation exhibited lower expression in old trees, those associated with the final stage of the aging process showed no difference in expression between young and old trees. This finding suggests that while growth slows, ginkgo biloba lives so long because it’s developed a perfect balance between growth and aging.
The trees’ biggest threat? Stress (one can relate). The older the tree, the greater its ability to adapt to changing environments, owing to persistent expression of a large number of resistance genes in addition to accumulation of antimicrobial and antioxidant protectants like flavonoids. But even the ginkgo has not been immune to climate change, which is causing the trees to shed their fruit later every year.
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As days become shorter and temperatures fall, the petioles, or stems joining leaves to a stalk, of most deciduous trees form a protective scar between the leaf and the stalk at different rates across the tree that causes leaves to drop individually. Ginkgoes, on the other hand, form those scars all at once, resulting in one day per year when tree-lined streets in Northwest DC suddenly come to resemble a sparkling forest floor. Among the leaves, sometimes, when a female tree hasn’t been sprayed with a pesticide at the right time, will be her fruit—called berries that look something like a cross between a green grape of the wine variety and a white apricot.
They smell awful, so every spring, the Urban Forestry Division sprays female trees across the District, but because it can be difficult to time properly and the treatment isn’t always effective, it has implemented a Female Ginkgo Tree Removal Policy allowing property owners to decide to petition for the removal of one or more trees. It promises to replant them with different trees, yet ginkgoes make for superior urban trees, offering shade and resilience to ever-increasing environmental stressors such as increasing levels of carbon dioxide.
In fact, the Smithsonian Institution has issued a call for leaf samples for its Citizen Science: Leaf Surveyproject, which it will use to study climate change. Not only do ginkgoes serve as a window to the past by providing a record from over 200 million years ago through to the present, but the secrets within their leaves might also allow us to better plan for the future. Scientists can analyze the relationship between carbon dioxide and stomatal index, or the optimal number of “tiny openings on leaves’ surfaces” needed to facilitate the exchange of carbon dioxide with oxygen and water. That information can help us to predict how warm the planet may grow to be and, I’d argue, to understand how different built environments affect nature.
From “Paleobotany: A Sketch of the Original and Evolution of Floras” by Edward W. Berry, p. 356 of the Annual Report of the Board of Regents of the Smithsonian Institution, 1918.
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It can also help us to understand ourselves. Native to China and cultivated starting around 1,000 years ago, ginkgoes were brought to Japan in the late 17th century, where the fan-shaped leaf came to symbolize longevity, and to Europe in the mid-18th century.
They have persisted in Asian art as well as Art Nouveau, both styles represented in the Smithsonian’s Freer and Sackler galleries. From China, in the Freer Gallery of Art is The Bodhisattva Mile (Sanskrit Maitreya), seated in “Pensive Pose” (Northern Qi dynasty, ca. 575), the Buddha’s Dragon Tree depicted as a ginkgo. In the Arthur M. Sackler Gallery is Reminiscences of Nanjing: Old Gingko at Mt. Chinglong (Qing dynasty, 1707). From Japan, in the Sackler Gallery, is Crow and Ginkgo Leaves, from the series Seitei’s Flowers and Birds (Taish? era, 1916).
Now, in 2020, amidst a global health crisis and an environmental one too, the ginkgo continues to serve as a symbol of longevity, a reminder of the movement of time. It also reminds us that as participants in the world through which time moves, we will endure. We will learn how to live in a world where COVID-19 is an expected part of life. But that endurance also engenders a responsibility to ensure that world is one in which we’d be comfortable waking up and realizing where we are.
With longevity comes unknowing. The onset of COVID-19, with its watch-and-wait requirement, has shown us we can’t predict the future with certainty, and in this context the ginkgo might be considered, above all, a symbol of humility. It has adapted, it has endured, and still it protects us—providing urban havens, sources of wonderment, and scientific information we can use to reconstruct our changing relationship with the world around us.
That is our role now: to assume humility, recognize our unknowing, and take an honest assessment of our actions using the knowledge we are learning. With reverence, we might look to the ginkgo as our past and future, and to this moment as an opportunity to protect the environment and ourselves.
Freeing ourselves from perpetual striving, can we seek that balance between growing and slowing down that the ginkgo has refined naturally and over millennia? Taking pause, can we find the will to finally realize a wholeness within ourselves and with the natural world?
Hannah Nelson is an editorial strategist at the Society for Neuroscience. She holds a BA in English from the University of California, Santa Barbara, and has an appreciation for narrative journalism, botanical illustrations, wooded areas, and the flora of DC.