A tree grows in Washington... and everywhere
A plant from 1785 has created a modern-day ecological threat
Recently, a few men in uniforms gathered outside my house in Washington, D.C., so I went outside to see who they were and what they were doing.
It turned out they were from the office of the city arborist, and they were trimming trees to ensure they didn’t hit the electrical wires. (D.C. has an entire squadron of arborists, I learned, assigned to each ward of the city).
This was fortuitous timing, as I had been having an arboreal issue of my own. There was a plant in-and-around my property that I was not able to get rid of. I whacked it; it grew back. I sprayed it; it grew back. If I touched it with bare hands, I got a rash. I was worried it might be poison sumac. I pointed out the plant to the arborist.
“That’s Tree of Heaven,” he told me.
“Tree of Heaven?” I asked.
“It’s invasive,” he continued. “See that? That’s Tree of Heaven. And that? That’s Tree of Heaven, too. They’re everywhere. And we can’t get rid of them.”
The arborist and I chatted for a few more minutes, then he went on his tree-whacking ways. Relieved that it was not poison sumac, I was left with a new curiosity: what was Tree of Heaven, and why was it so hard to get rid of?
It turned out to be a more interesting story than I envisioned, so allow me to tell you an abbreviated version in this week’s newsletter…
Our story begins with Mr. William Hamilton of Philadelphia.
William Hamilton was an 18th century man of letters. Born into a wealthy and prominent family in 1745, Hamilton never worked a day in his life. He lived “the life of a leisured, landed gentleman,” as author Catherine E. Kelly has noted, his principal occupation being the management and manicuring of his family gardens.
Those gardens happened to be at The Woodlands, a grand and gorgeous estate outside Philadelphia overlooking the Schuylkill River. Hamilton assumed ownership of the Woodlands in 1760, and almost immediately sought to create an estate on par with those in Europe. A noted Anglophile—Hamilton took the side of the British in America’s war for independence—his dream was to make The Woodlands rival the gardens that were famous in England.
So, during a 19-month trip to Great Britain from 1784-1786, Hamilton toured the regions of the British countryside known for picturesque landscape gardens seeking inspiration for his own. He acquired and shipped home exotic species and plants from around the world, including “a number of curious Flowering Shrubs and Forest Trees” as he wrote at the time.
One of those trees was a species native to China called the TREE OF HEAVEN.
With his actions, Hamilton introduced the Tree of Heaven—also sometimes referred to as a Chinese Sumac—to the United States.
What he could not have foreseen was that 238 years later the Tree of Heaven would become one of the most invasive plants in the U.S. It has been classified as an ecological threat and as an “agricultural pest” by arborists nationwide, spreading to 42 states. A prolific seed producer—one tree-of-heaven can produce up to 350,000 seeds in a year—the tree has overrun native vegetation, taken over crop fields, overcrowded forest openings and become a fixture of American cities. Those trees that impossibly grow in every vacant parking lot, or on the side of every highway? Those are Tree of Heaven, brought to our shores in 1785 by a gardener seeking to impress his European friends.
Native to China, the Tree of Heaven that Hamilton acquired in England is notated in ancient Chinese texts. In Chinese it is known as Chun Pi; in Latin it is classified as Ailanthus altissima. Its bark has medicinal properties, and has long been used in Chinese medicinal practice. When diluted and extracted through a process called decoction, it can treat diarrhea, dysentery, cramps, asthma, ulcers and heart palpitations. It’s even thought to have antibacterial and anti-parasitic properties.
Those properties derive from the plant’s toxicity. Its pollen is highly allergenic, and its leaves are toxic to domestic animals. Farmers and gardeners can develop rashes when cutting down the trees, and the plants have a funky smell that can cause headaches and nausea. The roots actually have chemicals that kill the roots of other plants, and they are so powerful and destructive that they’re known for damaging building foundations and destroying sewer lines.
TREE OF HEAVEN? More like the TREE FROM HELL.
It is the aggressive roots that allow Ailanthus to be extremely tolerant of poor soil. Such is why they can quickly colonize roadsides and grow out of seemingly impossible cracks in pavement. That capability was immortalized in the 1943 book, A Tree Grows in Brooklyn, written by Betty Smith. The opening page of the book describes Francie Nolan’s only tree in her Williamsburg, Brooklyn yard:
“It had pointed leaves which grew along green switches which radiated from the bough and made a tree which looked like a lot of opened green umbrellas. Some people called it the Tree of Heaven. No matter where its seeds fell, it made a tree that struggled to reach the sky. It grew in boarded-up lots and out of neglected rubbish heaps and it was the only tree that grew out of cement.”
Is it a straight historical line from William Hamilton, to Betty Smith, to the D.C. arborist outside my door? Not exactly. The story of the Tree of Heaven has, in fact, a number of other characters.
Hamilton was very well connected among elites in the early republic. He exchanged personal letters with George Washington, James Madison, and Thomas Jefferson (to name a few) on matters of groundskeeping, botany, and gardening. Hamilton was even selected by President Jefferson to receive seeds from Lewis and Clark during their voyage to the Pacific in 1804-1806. His horticultural collection was vast—“there was not a rare plant in Europe, Asia, Africa, from China and the islands in the South Sea, of which has had any account, which he had not procured,” The Woodlands website says, quoting a contemporary letter—and after Hamilton acquired his Tree of Heaven other influential men followed suit. By the middle of the 19th century, the tree was available for purchase in many American nurseries.
Also during the 19th century, Chinese immigrants arrived in the U.S. It is believed that some Chinese immigrants brought Tree of Heaven seeds with them, using the plant bark for medicinal purposes to help alleviate the hardships of working on the railroads and in the mines. It is surmised that one of the reasons the tree has invaded so many abandoned mines in the western U.S. is because of its past presence among Chinese laborers.
By the 20th century, Americans seemed to have already developed a love-hate relationship with the plant. In 1918, a fiction book titled Tree of Heaven was authored by May Sinclair. In the book, the tree is (not surprisingly) depicted as a solitary plant growing amid a broken brick wall. In 1925, the Associated Press described the tree as a “noxious plant” that was slated to be “condemned.” However, that same year the Pennsylvania Department of Forests and Waters determined that the bark could be suitable for paper fiber, and could help to “solve the problem of wood shortage for paper manufacturing purposes.” “As a result,” the AP continued, “the department will plant thousands of ailanthus (tree of heaven) seeds which in 25 years should produce 43.2 cords of wood per acre.”
What those plantings produced, instead, was an intractable pest that has now taken over the American landscape; pervasive, persistent and proving impossible to contain. Elimination of Tree of Heaven is extremely difficult and time-consuming due to the high seed count, fast growth and fierce root systems. What started as an ornamental curiosity for a single man in 1785 has become a nationwide epidemic—and a real pain-in-the-you-know-what for me.
What should we make of this peculiar history?
At the same time I was writing and researching this post, the U.N.’s Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES) released a report stating that invasive species pose an under-appreciated global threat. The report says that there are more than 37,000 alien species introduced to regions around the world by human activity, with an estimated cost of $423 billion annually, a rate that has been rising exponentially since 1970.
The implication by the U.N. is that this is a modern-day problem, an outgrowth of globalization in the 20th and 21st centuries. But, as historically literate citizens, we know that some of these invasive species have much longer histories that stretch back much further. Indeed, a graph in the IPBES slide deck shows that the accelerated trends of invasive plants and fungi actually began in the 18th and 19th centuries. It was a very globally interconnected world back then, too. Some invasive species were not caused by duplicitous actors or blindly capitalistic ambitions. To put it very simply, when people traveled, they brought things with them, either to impress their friends or to keep alive medicinal traditions from their ancestors. Those things stayed and found new roots—literally.
If it had not been William Hamilton who brought the Tree of Heaven to the U.S., others surely would have—either for ornamental purposes or medicinal purposes. Probably the only way to eliminate invasive species would be for humans to not travel, which seems unlikely, especially at the U.N.
If there is any lesson from this history, then, perhaps it is simply this:
Think carefully about what you do today. It could create a massive problem for someone else down the line.
Have a good week,
-JS
Interesting, scary story, and great message.
Hello Jason,
I'd say this "Tree in Washington" is so romantic to read as fun, but necessary to read as food. Thank you so much to share this writing with people, "paywall" is prohibitive and discriminative, to the have-not.