Does anyone know why some maples hold onto their dead dried out leaves while most maples drop their spent leaves in the Fall? My Takinogawa is completely leafed out and yet it still has quite a few dead dried up leaves from last year. I have a few other maples that do the same thing and I have often wondered why. What benefit would holding onto the old dead leaves have for some trees? I have tried to read about this and I think abscissic acid is involved in dead leaf retention among other things but if someone knows anything about this, I would love to hear your thoughts.
Mike, I've noticed that attribute (marcesence) and wondered if it serves any purpose. 'Waterfall' holds many complete and shriveled leaves and often A.S. 'Palmatifolium' holds just the base of the petiole tightly around the bud. Could persistent leaves be useful as insulation against wind and sun for the bud? Could they veil the bright color of the bud camouflaging it from bud eating critters? It happens with Oaks and Beeches so there must be theories or legit explanations out there. It's very windy here. This is in wiki: Benefits In plants, marcescence is considered a juvenile characteristic because it is more common on younger trees and on the lower, more juvenile, parts of older trees. One possible advantage of marcescent leaves is that they may deter feeding of large herbivores, such as deer and moose, which normally eat the twigs and their nutritious buds. Dead, dry leaves make the twigs less nutritious and less palatable. Marcescent leaves may protect some species from water stress or temperatures stress. For example, in tropical alpine environments a wide variety of plants in different plant families and different parts of the world have evolved a growth form known as the caulescent rosette, characterized by evergreen rosettes growing above marcescent leaves. Examples of plants for which the marcescent leaves have been confirmed to improve survival, help water balance, or protect the plant from cold injury are Espeletia schultzii and Espeletia timotensis, both from the Andes.[3][4]
Gil, great reply. I was unfamiliar with there being a term "marcescence" for this characteristic though I should have figured as much because botany has a term for everything. Another item to add to my research basket. Will let you know what I find out. Thanks for the heads up. Mike
It seems to be more common on late summer shoots which would support this idea since those buds are less capable of protecting themselves. Unfortunately the stems are often not either.
this is a complete anectode but the I notice that the same trees that don't give me great fall colors seem to be the same one that just brown up and seem to hang around all winter
Good question, and one I've wondered about too. I've never seen a reliable explanation (and I never heard the term "marcescent" before either). There are two kinds of leaf retention, I would say--pathological and nonpathological. I used to think that abcission of leaves was a passive process--when the leaves die, they fall off--but it isn't. A healthy tree MAKES its leaves fall off--it's an active process, and when something interferes with the process, the leaves don't form an abcission layer. So if a branch breaks during the summer, it doesn't lose its leaves in the fall. I've noticed the same thing if a branch dies from a verticillium-ish disease--in December, it's the only branch on the tree with leaves. On my palmatums and japonicums, I only see this when a branch is sick or when they got hit by a frost while still in green leaf. Then there's carpinifolium, which is the only nonevergreen maple I grow that hangs on to its leaves when it's healthy. I have no idea why--maybe it's a protection against something that went extinct long ago. One curious thing is that the leaves dangle off the tree in winter--the petiole breaks, but the leaf remains on the tree, as you can see in the second photo. It must slow the wind a bit, so a sustained wind in cold weather would do less damage. Dan
I have always thought it had to be something pathological because my maples may hold their leaves one year, but not the next. I remember one year A. palm. Shishigashira held all its leaves and I decided it looked gross, so I took them off by hand. Then (after the fact, of course) I decided to ask on UBC if I should have done that, I was warned that I shouldn't because it might damage the buds under the leaf. Luckily, it didn't seem to do any damage, but I have never removed any since. The times it's really bothersome is when I wrap some with floating row cover in the winter and they are still holding leaves. I'm afraid it might lead to fungal problems with dead leaves getting moist sitting around the branches. Kay
I really appreciate this thread. I've never stopped to think about it, I've just felt the dead leaves were ugly and plucked like crazy every year. Hmm. Thinking about it more rationally now I realize that the trees that "needed" leaf removal most are ones I'm concerned about for one reason or another. Very interesting.
Snip the leaves off with a small scissors, but leave the petiole attached. This way, you will protect the buds, but remove the visual clutter of dead leaves.
