Marcescence

"Retention of dead plant organs that normally are shed."  Etymology from Latin "marcere" = "to wither." I can't think of any related words.

This phenomenon, when leaves fail to fall, is called marcescence. Most evident on all the oaks around the metro, it's an explainable but puzzling occurrence. At the petioles, the point of attachment to the tree, hormones flow back and forth. As the days shorten and temps fall, the amount of one in particular, auxin, is reduced. The area becomes sealed and a digestive enzyme helps to release the leaf. In fancy science talk, this all happens in the abscission zone.

Yet it doesn't always go as planned in the abscission zone. Although it is not known exactly why, some leaves on certain tree species remain through winter albeit in a brown and lifeless form.

This phenomenon is quite in evidence in the woods behind our house, where the oak trees have clung to their leaves through a long cold blustery winter.  As soon as the new buds form, the old leaves will finally drop.

I wanted to illustrate this post with the famous cartoon - I think it's Charlie Brown raking leaves but one leaf remains on the tree. I couldn't find it on the web. Perhaps it wasn't Charlie Brown. Some other cartoon???

Photo credit pyrahna.