Each city has one or two trees that grow best in its climate and suits best in its urban fabric. When you see roads canopied by rows of huge trees, bifurcating at the trunk, you know you are in Nanjing. The trees are oriental planes (Platanus orientalis), the characteristic tree seen on the sides of every street, in every neighborhood of the former capital. In summer, giant green canopies on both sides of a typical Nanjing street interlace in the middle, like two arms crossing into an embrace, shading people and traffic. The warm, gentle green giants have been nourishing Nanjing, and nurturing each Nanjinger. When you see small trees with delicate, alternate leaves in many leaflets, you are in Beijing. The tree is Japanese pagoda tree (Styphnolobium japonicum), which is unfortunately named because it is native to China, and introduced to Japan. The pagoda tree flower is one of the 50 core essences of Chinese herb medicine, and its Chinese name has a mythological origin. The pagoda tree is one of the two signature trees of Beijing. The ginkgo is the other one. The gingko is a living fossil, quite an unusual plant whose presence on earth can be traced to the Permian. Although the gingko is cultivated all over the world, the only natural habitat for the gingko is Beijing and its surroundings on the same latitude. The gingko’s natural specificity interwoven with the city officials’ programming efforts creates a golden autumn in old Beijing alleys when the trees all dress themselves up in cascading, pure lemon yellow leaf fireworks. The golden gingko and the dark-barked S. japonicum have delineated the identity of Beijing.
The urban planners of Nanjing and Beijing have followed nature’s call in the choice of their city trees, not imposing artificial selection on altering the existing nature of the cities, but accentuating the natural condition. The trees’ nativity and the city’s municipal design had together created a beautiful and long-lasting urban ecosystem and streetscape, and they have been successful in making the signature tree species known to the people living in the city. Beijingers are proud of their trees! Oh my! When I see a Japanese pagoda tree, I immediately feel a connection — it may be a psychological, social, or ecological connection to my city. As an avid traveller I have seen gingkoes in many cities abroad, and every time I encounter one, I shout out: “it is MY gingko!” I don’t say it is “a gingko,” I am used to saying it is “my gingko.” Often people don’t perceive how much information their word choice contains. I realized that certain trees to certain people have become a cultural tie to a city, a type of city identity that I call “arboridentity.” In the age of globalization, gentrification, and modernization, cities tend to grow to be alike, instead of growing to be unique. On the road to conformity, some cities are losing their traditional identities or altering them. While it is a controversial process, arboridentity remains stubborn in the wave of change since native vegetation has an unsurpassable affinity to the land it owns. Already more than a natural phenomenon, trees in certain cities have become an embodied cognition, profoundly embodied in this area’s history, atmosphere, climate, hydrology, folklore, and everyday language.
When I came to America, studying at Duke, I was quick to discover, with some surprise initially, an aspect of American culture that I wasn’t aware of before. Americans don’t know their trees. Beside a small number of tree huggers and outdoor hobbyists, most inhabitants of a city can’t name the species of their prevalent trees. Tree identification is perceived in the expert realm, not culturally embedded. There are exceptions too. If you ask a random Durhamite, what kind of tree is the large evergreen with smooth leaves and snow white, lotus-shaped flowers? You will probably get the answer “it is the southern magnolia,” which sounds just as magnificent as its flowers look. It is one of the most common trees in Durham, North Carolina, and many southern states. But I’ve noticed that in the North Carolinian cities the southern magnolia functions primarily as an ornamental backyard tree, whereas it rarely appears on the street side or in public spaces. The magnolia is the opposite of low-key, but has a particular, showy, flamboyant character that may create a spectacular alternative effect if planted along streets and incorporated in the city view. While it is an attractive hypothesis, we will need more information on how the tree alters landscape both above and underground and how it manages hydrology before proposing to establish it as the city tree or state tree of any place.
If small cities like Durham really want to fasten their process of development, they will inevitably face the issue of tree choice, because urbanization requires intentionality to every detail. Hypothesize that we hired a team of researchers, and surveyed native-born Durham inhabitants with questions: what are the tree(s) in your memory of childhood? What tree(s) first come to your mind when you think about Durham? Have you experienced encounters with familiar trees that brings you feelings of home when you traveled outside of Durham? Synthesizing the results with gardening and ecology experts’ analysis, we can be intentional and thoughtful of the big picture in making decision on how to form and express an arboridentity of the developing Durham. Since the arboridentity has always been latent in the area, but never has been articulated, the underlying insects and birds local to the area will stay compatible with the new municipally established arboridentity. Not limited to trees, there are many currents, forces, elements, and systems always existent in a city but never articulated. In the ideal city I envision, one of the major goals is to articulate the unarticulated.
To articulate is to delineate, to educe the essence from a place, without exerting arbitrary forces upon it. Too often decision makers start from the question what trees cope best in the climate, whether people need big shades or small shades, whether planting this species of tree does damage to the construction of the site, etc. While all of these are valid questions and some are necessary to every design, I think we should start by asking this first question: what has been already existing in the city, and what is embodied in the city dwellers’ cognition? To educe is to bring the essence out and make it pronounced. I spent my first two college years only knowing the spring and fall of North Carolina. Due to an internship in the summer between my second and third years, I stayed two months in Raleigh and I was stunned. Raleigh by the way is nicknamed the Oak City. Having never experienced summer in North Carolina, for the first time, I witnessed the passion of the Oak City — fiery red and pink crape myrtles blooming like a beautiful parade along city streets, roads, they were everywhere. Being continuously amazed on my daily commuting trips, I realized how impactful trees can be to the perceptual, atmospheric and cultural qualities of a city. And on the other hand, it made me ponder why I hadn’t noticed such a breathtaking arboridentity before. Coming from a large metropolis, I easily falsely assumed that the Raleigh-Durham downtown area was duller than it actually is. That summer of fiery crape myrtles opened my eyes to a kind of arboridentity that is wildly seasonal, and perhaps a more important insight is you can never fail to discover the excitement of a place as long as you’ve stayed there long enough. I was also incredibly lucky, I admit, to have traveled extensively which fostered a sensitivity to arboridentity and other parameters of uniqueness that differ across cities. So it is important to articulate arboridentities through investigation and implementation, to make them salient to a wider population. That summer, that awakening of Raleigh’s passion, was unforgettable because this particular facade of city identity was unseen in other cities. Crape myrtles in Beijing are more sparsely planted, primarily a small residential yard plant, and Chinese prefer light pinks and light violets to bright saturated varieties. Crape myrtles are not unique to Raleigh, but this passionate, seasonal carnival is. When you live enough time in a city, you will feel an irresistible cry from the land: “Love the trees of the city you dwell upon!” The crape myrtles that made me love Raleigh, which many people always pass by but rarely see, are the awakening of the city’s passion!