by David Hopman, ASLA, PLA

All cities in the United States have undesigned areas that develop what is called “spontaneous urban vegetation”—plants that establish themselves without human intervention or planning. These areas can be large, such as abandoned or vacant building lots, former farms and ranches, and river corridors. They can also be small opportunities for plants and plant communities in sidewalk cracks, between paving and buildings, or anywhere enough soil has accumulated to allow the sprouting of seeds, as was the case on New York’s High Line elevated railroad before it was so famously developed into the urban amenity it is today.
In well-developed cities, 5-10% of the total vegetation or more can be spontaneous. In Detroit, the amount of area abandoned to this undesigned vegetation is about 40% as the city has depopulated and thousands of homes have been removed.
Spontaneous urban vegetation has been widely touted by scientists and landscape architects for its environmental benefits that include but are not limited to:
- excess nutrient absorption in wetlands,
- heat reduction in paved areas,
- erosion control,
- soil and air pollution tolerance and remediation, and
- food and medicine for people.
However, there has been very little discussion, or appreciation, of the role that this vast amount of urban vegetation can have on native pollinators.