The Day the Gingko Leaves Fell

Nov 6, 2012

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[youtube=http://www.youtube.com/watch?v=B8IkDKsmee8&w=600&rel=0]

This morning I awoke to see the Gingko (Ginkgo biloba) shedding it’s fan-shaped leaves. First I noticed the golden carpet ringing the tree trunk, and then I headed out and stood underneath the boughs to hear the last tumbling gingko leaves.

Gingko Leaves Retrospective

Here’s what I wrote on November 3, 2010 on my blog when the gingko leaves let go and I first photographed the peculiar phenomenon.

Each autumn the leaves of an enormous old Ginkgo Biloba tree in our yard retain their leaves until the frigid end. They’re among the last leaves to fall, and they remain green until just a day or two before cascading down. And when they decide it’s time to let go, they all do it at once.

An enormous canopy of a tree reaching about 100 feet tall covered in thick foliage one day and naked the next. It’s dramatic. And slightly surreal. (virtualDavis)

Gingko Leaves 2012

The gingko leaves had transformed from green to brilliant golden in the last few days, so I have been anticipating their fall, but the change is so stark and so sudden each year that I can’t help but stop and wonder about this mysterious tree “with no close living relatives… similar to fossils dating back 270 million years.”

English: Ginkgo leaves shown in their fall col... — Ginkgo leaves, fall color (Wikipedia)

During autumn, the leaves turn a bright yellow, then fall, sometimes within a short space of time (one to 15 days). (Wikipedia)

But why? Why (and how) does this prehistoric species retain its chlorophyll-rich leaves so much later than other deciduous trees? And why do they drop so suddenly, so precisely — the entire vast canopy shed in a matter of hours — after a deep frost?

If it were the first hard frost or the most severe frost to date, it would make sense. But last night was neither. And yet almost all of the leaves have cascaded down to the ground over the last few hours.

Gingko Leaves Mystery

Can you explain the gingko leaves dramatic behavior? Please post your hypothesis (or scientific solution to this mystery) in the comments below. Thanks.

Comments

4 responses to “The Day the Gingko Leaves Fell”

Laura Smith

November 6, 2012

George, it took a bit of searching but I found your answer! http://articles.chicagotribune.com/2007-12-09/news/0712070169_1_leaves-ginkgo-trees I think you must be on the very upper end of the zone for them. We’re half a zone colder here on Willsboro Bay but w/Climate Change I think I might give them a try.

Reply
1. virtualDavis
  
  November 6, 2012
  
  Thank you, Laura! Impressive sleuthing. According to the post you located in The Chicago Tribune, “Why does ginkgo lose all its leaves at once?”, the crux of the matter seems to be that, unlike maples and other deciduous trees which gradually produce scar cells to protect their petioles their health when leaves fall, the gingkos do this all at once:
  
  “The petioles of ginkgo leaves form the protective layer simultaneously and wait for a hard frost to trigger all leaves to drop at the same time, which results in a lovely shower of golden leaves.”
  
  Fascinating. But why? I’m still curious what is different about the gingko that allows it to undertake the process for all leaves concurrently…
  
  Reply
Jim Swindle

November 24, 2012

It may have something to do with the fact that, unlike almost all other trees with leaves, the Gingko leaf does not have a central vein. Just what it would have to do with that, I don’t know.

Reply
1. virtualDavis
  
  November 26, 2012
  
  Hmmm… No central vein? Curious. Though I’m not sure what to infer. Thanks for your contribution to the puzzle, perhaps it’s the missing clue! 🙂
  
  Reply