Spying on Sycamores

Back last spring, I watched to see the first buds on a rank of sycamore trees that march down the center of Indian Hill Boulevard. Something strange happened. About half the trees turned yellow green, then darker green, then leafed out fully, leaving the other half still looking lifeless. I noticed that the leafed out group had gray, rough bark on their trunks while those still quiescent had white trunks, lightly mottled with gray and green blotches. A week went by, then the second crop of trees began to green and they fully leafed out too. At first, I conjectured that the sycamores were all the same type and there had been some kind of "beautifying" attempt to remove the gray bark from the white ones, making them slow to lift nutrients to their branches. But the seasons have turned, and I've looked at the trees every morning when I drive to work for three fourths of the year, and their trunks haven't changed. Now, I'm waiting to see if the two groups will lose their leaves at different times. Sycamore is stingy with its leaves. They turn a browny-yellow and hang on a long time. I remember, though, that last spring not a one had any leaves, so they'll go some time. A Santa Ana wind will come along to encourage them. Will they all go together when they go? I'm watching.