Story and photos by Georgia Silvera Seamans, Washington Square Park Eco Projects Director
With diameters at breast height (DBH) ranging from 15 to 25 inches (38 to 64 cm), and given that the DBH-to-age conversion rate is 4.0 for the species, we know that Ginkgo biloba trees in Washington Square Park are 60-100 years old. Ginkgoes were introduced in the U.S. in 1784, according to Arnold Arboretum Senior Research Scientist Emeritus Peter del Tredici. Botanist and plant collector William Hamilton planted two trees on his Philadelphia estate and gifted a tree to John Bartram in 1785; a male ginkgo in Bartram’s Garden is the oldest living tree of its species in the U.S.
The Ginkgo biloba has a long history in New York City, too. According to the New York Times archives, a parent plant of the famous ginkgo planted in City Hall Park in 1929 was brought to the U.S. in 1857. The City Hall Park ginkgo was renamed the “Walker Tree” in honor of Mayor James J. Walker, but sadly this ginkgo died and was cut down in 1937. Another notable ginkgo in the city is the memorial tree planted at the General Grant National Memorial in 1897.
Everyday New Yorkers also had experiences with Ginkgo biloba. New York Times archives show that the species was included in mid-20th century tree planting campaigns alongside what they called “Oriental plane” (syn. London plane tree), Norway maple, elm, and linden. (Ginkgo was even recommended as an alternative to London plane trees.)
Another significant ginkgo event in the city occurred in 1956 with the gift of 2500 ginkgo seeds from a Tokyo-based international friendship group called Friends of the World, Inc. The seeds were grown out at the Park [sic] Department nursery on Rikers Island. Unfortunately, the tree nursery on Rikers Island was destroyed over the course of two decades, beginning in the 1970s, to expand the prison complex.
Although the contemporary provenance of Ginkgo biloba is East Asia—plentiful around temples—the species grew in North America during the Jurassic period, 180 million years ago.
The ginkgo is a quintessential urban tree. It is tolerant of air pollution and poor soils as well as the diseases and pests that have decimated our most beloved forest and urban trees. In the borough of Manhattan, more than 9 percent of all trees are ginkgos. According to NYC Street Tree Census data, Ginkgo biloba is also the 9th most dominant street tree species citywide.
Before we consider one of the most controversial features of the ginkgo, let’s look at other defining characteristics of the species. The golden fall color of Ginkgo biloba is stunning. Equally dramatic is the ginkgo’s senescence, which Peter Crane, author of Ginkgo: The Tree That Time Forgot, writes is “the most synchronized leaf drop.”
Clockwise from top left: Spur shoot, aka short shoot: note no notches on leaves; ginkgo leaf with no central notch; leaf with notch of medium length; deeply notched leaf; double-deeply notched leaf!
The specific epithet of the species, biloba, is a clue to a reliable field mark: many of a ginkgo’s fan-shaped leaves have two lobes, with a notch at the apex of variable depth. Not all of a ginkgo’s leaves are lobed, however. Peter Crane notes that ginkgo leaves that emerge from long shoots later in the season are generally lobed in contrast to the frequently unlobed leaves that emerge from short shoots.
Many of the ginkgoes in Washington Square Park are female. The species is dioecious, meaning that female and male reproductive structures are born on separate plants. However, Crane points out that there are “leaky males”—male trees that bear seed. Ginkgo biloba produce naked seeds that are covered by an apricot-colored, fleshy seed coat known as sarcotesta. When this seed coat is mature and then crushed, it releases an odor that some people find very objectionable (stinky)! So much so, that since 2004, the NYC Parks Department only plants male cultivars.
Clockwise from top left: Maturing ginkgo seeds on a tree in Washington Square Park; newly fallen ginkgo seeds; harvesting fallen seeds in Washington Square Park; ginkgo seeds with and without the soft sarcotesta coating; cooked ginkgo seeds in the author’s kitchen.
A more pleasant way to interact with mature ginkgo seed is to eat them! After many years of knowing that the seed is edible and watching people harvest it in Washington Square Park, I finally foraged in fall 2019 with a couple of tips from other foragers on the scene. I used a plastic bag to pick up the seeds and collected seeds that had less sarcotesta on them. I washed the seeds at home to remove all the flesh then cooked them in olive oil and salt until the shells cracked. After the shells cooled, I cracked them fully open to expose the pistachio-green colored “nut.” In a word—delicious!