Photo by Annabel Renwick.
The silver-grey granite medallion marking the 36th parallel north—the circle of latitude approximately thirty-six degrees north of the equator— has been relocated within Duke Gardens. The marker was originally placed in the Blomquist Garden of Native Plants to celebrate the 60th birthday of William Louis Culberson (1929 – 2003), the Duke Gardens director from 1978 – 1998 and a Duke university botany professor and lichenologist.
For many years, the medallion was ‘off the beaten track’ lying in the backwater of the Blomquist Garden adjacent to the Sunny Pond. In the past year, this area has become a major attraction at Sarah P. Duke Gardens thanks to a major renovation including an inviting new boardwalk and stunning seating area. The plantings surrounding the pond represent some of the plants from the United States’ southeastern coastal plain, with special emphasis on carnivorous plants.
While working on this project, we realized that the 40-year old stonewall around one side of the Sunny Pond did not comply with the current safety code requiring a 40-inch barrier across the length of the wall to prevent falls. As adding a fence or other barrier would compromise the wall’s integrity and change the aesthetic of the area, we decided to remove the adjoining path permitting visitors access to the boardwalk from both sides of the pond. However, removing this path also meant no access to the 36th parallel medallion, so it had to be moved to a different location still on the 36th line of latitude north.
Using GIS technology, it’s possible to pinpoint a specific spot on the planet within centimeters. So it came as a surprise to learn that the original placement of the medallion was around 50 feet north of the true 36th line of latitude. Fortunately, we were able to move the medallion to a new and more accessible position on a plinth adjacent to the new storm water conveyance system, where it is more easily visible—not to mention directly on the line it is supposed to mark.
What started out as a health and safety problem ended up raising far more existential questions. Does it really matter that the medallion marking an otherwise invisible line has sat in the wrong place for 37 years? In the grand scheme of things, probably not, as it was always intended to be commemorative rather than a navigational aid. Still, it’s satisfying to know that it is finally in the “right” place—but how exactly do we know where “right” is supposed to be?
Early civilizations across the globe independently recognized that tracking the sun’s movements across the sky over the course of a year could help them plan in order to survive the changing seasons. As a result, they went to great efforts to construct large structures like Stonehenge in the United Kingdom and Casa Grande in Arizona, which are thought to have served as observatories. At the same time,people have used celestial bodies to navigate the planet for millennia, with rudimentary lines of latitude appearing in some of the earliest maps to determine the user’s north-south position. (Lines of longitude, which run from east to west, are more difficult to measure accurately, as they require comparing readings from multiple locations across vast distances rather than single measurement in one place.) Today we can locate ourselves, using our cell phones, which rely on satellites in low earth orbit to provide the information needed for accurate geolocation. Without the coordinates provided by latitude and longitude, Google Maps and other location apps we take for granted wouldn’t exist!
Although they don’t calculate in the same way that humans do, plants have evolved the ability to detect their proximity to the equator and to the poles. Because latitude is directly linked to the amount of sunlight in a given place throughout the year (and thus the length of the winter), the same native plant species growing in Mississippi or Louisiana at 31 degrees north will continue to emergence and flower earlier than the same species that evolved 5 degrees further north. Likewise, the same plant species evolving and growing 5 degrees north of the 36th N parallel will emerge and flower later if brought to North Carolina than the local population of that same species around the 36th parallel. In that sense, the life cycle of every native plant growing along the 36th parallel is a marker of its existence, albeit far more subtle than our engraved stone medallion.