Something smells, and it may not be the ginkgo fruits.
Some Philadelphians have noticed ginkgo trees in their neighborhood acting differently this year. One Rittenhouse resident said the tree in her back yard has dropped leaves, but the seeds — which only grow on female trees and are known for a vomit-like stench when they fall and break — have held on longer than normal.
Others have noticed leaves staying on branches longer, or staying green instead of turning to their signature vibrant golden color.
“The trees usually turn yellow and drop one half of the leaves then the second. The ones on my block haven’t turned yet,” Dena Driscoll, a ginkgo enthusiast in South Philly, told Billy Penn.
“Is it me or do the ginkgo trees seem extra green extra long this year?” asked South Philadelphia artist Aimée Sigel in an Instagram post.
Ginkgoes have a unique trait: they generally drop their leaves all at once, rather than gradually over time, so it’s easy to notice when they’re even a little bit off schedule.
The differences people are noticing in Philly could be because of this year’s weather, said botanist Peter Crane.
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Philadelphia had record-breaking heat this summer, and started November with a string of unusually warm days, noted Crane, a ginkgo tree expert and president of Virginia’s Oak Spring Garden Foundation. However, the broader trend of ginkgoes dropping later and later in the fall has been emerging for decades, thanks to climate change.
While the shifting climate has caused problems for many species, the phenomenon of leaves remaining green or on the tree longer probably isn’t bad for Philly ginkgoes, per Crane. “It might even be a little advantageous,” he said, “because they’re still photosynthesizing while they’re on the tree.”
When a deciduous tree drops leaves in reaction to cold weather, a protective scar forms between the leaf and the stem that helps shield the tree from damage during the winter months. For many trees, that happens leaf-by-leaf, but for ginkgoes it happens near-synchronously.
Ginkgo biloba are native to China, and are known for being incredibly resilient. The species has existed since ancient times.
They’ve become numerous in certain cities throughout the U.S., where summers are hot and winters are cold. Many believe their debut on this continent was in Philadelphia — the big one at Bartram’s Garden in Southwest Philly is thought to be the oldest living ginkgo in North America, dating back to the 1700s.
That historic tree is usually the last of the garden’s several ginkgoes to drop its leaves each year, according to Mandy Katz, Bartram’s lead gardener and land manager. (It’s a male, so it doesn’t drop fruit.)
Bartram’s also has a row of female ginkgo trees at its entry — which have dropped their stink bombs.
“We would only be making guesses as to why [other] trees would not fully set their seeds and drop,” Bartram nursery manager Dan Feeser said. “We did have a drought-filled summer, so that could be a factor. Other factors could potentially be age or the health of the tree that influence a tree’s seed set.”
The fruit, while distinguished by its smell, is edible, and people in Philly sometimes forage it to cook in soups and rice.
Botanist Crane noted the trees do require a cold winter, so climate change may affect their ability to thrive in the U.S. South. That shouldn’t be a concern anytime soon in Philly, he said.
“It’s somewhat similar to the conditions in Eastern Asia, where they’re native to,” Crane said. “It’s a great place, and ginkgoes thrive in Philadelphia neighborhoods.”