ELi on Earth: When EL Ginkos Lose Their Leaves

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Monday, November 2, 2015, 12:31 am
By: 
Aron Sousa

Editor's note: This article originally ran last fall in a slighly different form.

The day after East Lansing gets a killing frost, residents will likely be treated to a rain of leaves from all the local ginko trees. Most types of trees lose their leaves over the course of several weeks, but ginko trees usually lose their leaves in a day following a hard frost. Below we provide a video taken last year during East Lansing's ginko-leaf rain.

The Gingo biloba is a tree not recently native to East Lansing but is found in earth’s fossil record relatively unchanged for 190 million years, with close relatives that date back to 250 million years ago. To give a sense of scale, the “age of dinosaurs” starts around 250 million years ago, just after the world’s largest extinction. Because of the glaciers that covered Michigan, you won’t find ginko fossils in East Lansing—the glaciers scraped away all the dirt from that era—although the tree did grow in areas of North America until about 9 million years ago.

All of the living ginko trees in East Lansing and the rest of the world are direct descendants of trees grown in central Chinese monasteries about a thousand years ago. It is not clear if there are any remaining “wild populations” of ginko; it may be that all remaining ginkos owe their existence to human activity dating back thousands of years.

Scientists organize life by grouping related species together and call the whole system “taxonomy.” Ginkos are in the Plantae kingdom and humans are in the Animalia kingdom. The Plantae kingdom is then broken down into divisions  (ginkophyta for the ginko) and the Animalia kingdom is broken down into phyla (chordate  for vertebrates, which includes humans).  The ginko has its own division separate from all the other plants and the Ginko biloba is the only surviving species of its division. In animal terms, this would be like there was only one remaining species of animal with a backbone—for example, imagine there were goldfish, but no mice or people or lizards. The people and mice of East Lansing are more closely related to each other than the ginkos and oak trees of East Lansing are related to each other.

The ginko does not flower, but the species does have male trees and that produce pollen carrying sperm and female trees with ovules. The pollen is carried by the wind, as happens also for conifers and fern trees. Unlike the sperm of ferns and conifers, a ginko sperm completes fertilization by moving with a whip-like tail (a flagellum) once it lands on an ovule. Once pollenated, the ovule becomes an embryo and the embryo matures into an edible nut. The covering of the ginko nut contains butyric acid and smells like rancid butter, so people prefer to plant the male trees rather than females in their yards and along their streets. The ginko tolerates pollution and street salt, and so is now a relatively common urban tree.  

The ginko’s leaves are commonly portrayed in art and ginkos are sought out for their unique fan-shaped leaves and intense yellow color in the fall. Unlike most trees, which lose their leaves over the course of several weeks, ginkos usually lose their leaves in a single day following a hard frost. The following video is of an 80-90 year old ginko in East Lansing losing its leaves on November 2, 2014. Turn up the volume to hear the leaves falling, and if you're on a computer, set yourself to 'view full screen."

 

 

Here's a photo taken the night of October 28, 2015, of a ginko near MSU's Eli Broad Museum.

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