Got Nature? Blog

Question: Often ginkgo trees will drop all of their leaves on a single day after a cold night. I thought that was going to be Monday at Purdue (left: leaves falling). But no, we’re at Wednesday now (right) and this one changed its mind. Anyone know how common that is?

Answer: It was a very peculiar fall. The overall leaf drop was one to two weeks later than normal at least. An October with weather more like September has likely had some impact on this. Individual trees will vary some on their leaf drop timing, probably due to their geographic origin (for planted trees) and individual genetic variation. The severity and timing of frost/freeze also influences strongly. As you can see, lots of variables!

Leaf drop is not solely dependent on temperatures. There is a process of dormancy the tree follows to properly acclimate in preparation for winter. One of these is leaf drop, but it must go through the process of developing an abscission layer between the petiole base and branch. Most likely, the tree didn’t drop leaves yet because this separation layer of chemicals hasn’t fully responded yet. We often see frozen leaves on a tree and later they fall, but this is the result of sudden extreme cold ahead of proper dormancy routines.

Resources:
Fall Color Pigments, Purdue Extension YouTube Channel
Why Leaves Change Color – The Physiological Basis,
Oak Wilt in Indiana, Purdue Landscape Report
Dog Days of Summer Barking Early This Year, Purdue Landscape Report
Tulip Poplar Summer Leaf Drop, Purdue Landscape Report
Be on the Lookout for Defoliated Viburnums and Viburnum Leaf Beetle, Purdue Landscape Report
Will my Trees Recover After Losing Their Leaves?, Purdue Landscape Report
What Do Trees Do in the Winter?, Purdue Landscape Report
Why Fall Color is Sometimes a Dud, Purdue Landscape Report
Alternatives to Burning Bush For Fall Color, Purdue Landscape Report
Start Preparing Trees for Winter and Next Year, Purdue Landscape Report
ID That Tree Winter Edition: Opposite Leaf Arrangement – Ohio buckeye, Red Maple, Purdue Extension YouTube Channel
ID That Tree Winter Edition: Alternate Leaf Arrangement – Black Walnut, Eastern Cottonwood, Purdue Extension YouTube Channel
ID That Tree Winter Edition: Alternate Leaf Arrangement – Honey Locust, Burr Oak, Purdue Extension YouTube Channel

Lenny Farlee, Sustaining Hardwood Extension Specialist
Purdue University Department of Forestry and Natural Resources

Lindsey Purcell, Urban Forestry Specialist
Purdue University Department of Forestry and Natural Resources