Three years ago I planted a small Trident maple in my front yard. It has done well, and is now about 6 feet tall and very bushy. It is planted in full sun, zone 6, in the Lehigh Valley of Pennsylvania.

When I first got it, I was surprised at the shape of the leaves, because they were not like pictures I had seen. Since then I learned that these trees seem to have a juvenile and adult leaf form. You can see the juvenile form here:

http://www.ubcbotanicalgarden.org/forums/attachment.php?attachmentid=8639&d=1129600209

Here is the adult form:

http://www.ubcbotanicalgarden.org/forums/attachment.php?attachmentid=8637&d=1129600209

This year, I saw the first adult form leaves on my tree. They are all on the inside of the tree, while the outer leaves are the juvenile form. It seems the adult leaves formed on three year old wood.

This fall, the outer leaves changed mostly to a maroon color, with some red and orange. Closer to the center of the tree, the leaves were all yellow. When I looked closer, I realized that all the adult form leaves were yellow, and all the juvenile form leaves were not...I can't find any exceptions.

It's possible the the microclimate near the center of the tree (more shade, more sheltered) can explain the difference in color, but what I see suggests it is more likely that the adult leaves color differently than the juvenile leaves in the fall.

This has me a bit worried, because I chose this tree largely for fall color, and I will be dissappointed if, as it gets older, more and more of the leaves simply turn yellow in the fall.

Has anyone else seen this phenomenon?

Alex