Many ginkgo trees are famous for dropping all their leaves at once – whomp! – after the first hard frost. There’s one tree on the Durham campus of UNH and people have kept records on its leaf-drop day since the 1970s. This year’s drop was the latest on record, as noted by UNH News:.
“This is only one tree, of course, but it shows that the growing season is being lengthened by climate change which is impacting the date of leaf fall,” said Serita Frey professor of natural resources and the environment. “Leaf fall in this ginkgo on UNH’s campus is triggered by a hard frost, and that didn’t happen until last Saturday night (11/11), which is very late for New England.”
Frey says the original focus back in the 70’s wasn’t on climate change. Everyone in UNH’s College of Life Science and Agriculture knew that the ginkgo tree dumped its leaves after the first hard frost so it became an annual contest for students in the Department of Natural Resources to try and guess the date. But a few years ago, she started looking for any data documenting the days the gingko leaf drops over the years to chart the progression. She did some investigating and found a log started back in 1977 by a secretary in the department and someone had been adding to it over the years. The document gave her a log that she added to a spreadsheet and created a chart to continue to monitor any changes. Frey has continued updating the data each year to track the leaf drops which are now happening later and later as the yearly hard frost has moved from October into November