The Taxonomy of the
Invisible: Counting Emerging
Urban Forests
Liz Danzico

School of Visual Arts | [e-mail]

those counting around him, they’re just “spontaneous.”

[ 1] N YC BigApps; http:// www.nycbigapps.com/ [ 2] Del Tredici, P. Wild Urban Plants of the Northeast: A Field Guide. Ithaca, N Y: Comstock Publishing Assoc., 2010.

[ 3] “Crypto-Forestry
and the Return of the
Repressed” BLDG
BLOG, 20 June 2010;
http:// bldgblog.
blogspot.com/2010/06/
crypto-forestry-and-
return-of-repressed.html
November + December 2010

[ 4] Pollan. M. “Weeds Are Us,” New York Times Magazine, 5 November 1989; http://michael- pollan.com/articles-archive/weeds-are-us/ [ 5] Janick, J. Horticultural Science (3rd ed.). San Francisco: W.H. Freeman, 1979.

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A spring 2010 app competition, NYC BigApps, brought together designers and developers to show how the city of New York could improve the way it provides information to its citizens. One of the 11 winning apps, “Trees Near You,” now helps users learn about the more than 500,000 trees that live on city sidewalks. For any area of New York City, one can discover tree species and calculate the environmental benefits that the trees provide, using publicly available tree census data. One of the most prevalent trees in the city, however, isn’t included [ 1].

Look out of any New York window, and you’re likely to see one, but you’d be hard-pressed to identify it. The reason: ailanthus altissima, or the “tree of heaven”—made famous by Betty Smith’s 1943 book, A Tree Grows in Brooklyn—hasn’t technically been planted by anyone. And because its placement was unintentional, it isn’t counted in street-tree inventories. Still, it grows, and at a staggering rate of five feet per year and up to 49 feet tall. It’s these sorts of plants, and their smaller relatives, that we refer to as “weeds.” Yet to one Harvard biologist and

Roots in Nomenclature

Peter del Tredici, a senior research scientist at the Arnold Arboretum of Harvard University and lecturer in landscape architecture at the Harvard Graduate School of Design, argues the wildlife that surrounds us every day often has an image problem—it goes unnoticed, unattended, and unvalued. “There is no denying the fact that many—if not most—of the plants…suffer from image problems associated with the label ‘weeds,’ or, to use a more recent term, ‘ invasive species.’ From the plant’s perspective, ‘invasiveness’ is just another word for successful reproduction—the ultimate goal of all organisms, including humans…. The term is a value judgment that humans apply to plants we do not like, not a biological characteristic” [ 2].

If it’s true that more than half the world’s people organize themselves in cities, then it’s our responsibility to understand and pay attention to the wild and unmanaged plants that grow up all around us. In the United States and other wealthy countries, more than

80 percent of people live in cities and suburbs. In these areas, wild plants are often ignored. They’re “crypto-forests,” as Dan Hill describes them: “Weed patches in which the earliest emergent traces of a thicket can be found; clusters of trees growing semi-feral on the edges of railroad yards; forgotten courtyards sprouting with random saplings unplanted by any hand: these are all crypto-forests” [ 3]. These urban spaces are a mix of the built, the wild, the human, and the cultivated. And as designers and service designers, we must approach all aspects of the system—the wild included—as equal contributors.

To understand better how to do so, we can look to the way in which “invasive species” has been defined. “‘Weed’…is not a category of nature but a human construct, a defect of our perception,” Michael Pollan points out [ 4]. On one hand, if weeds have had an image and perception problem, they are then “any plant growing in the wrong place.” Then, on the other hand, they are any plant “considered to be a nuisance in human-made settings and that grows and reproduces aggressively“ [ 5]. But a stronger posi-