My observant spouse and I were out walking recently, enjoying the spectacular colors of autumn, when he pointed out that the foliage of a Styrax japonica, Japanese Snowbell, was showing autumn color change from inside the canopy first before working its way to the outer leaves of the tree. He stated that most trees he sees follow the reverse pattern, and he wondered if this pattern is normal for this tree. I mentioned that our Styrax follows the same pattern – inner leaves change first followed by outer leaves. We contrasted it with our Ginkgo biloba, Jade Butterfly, which seems to change to its stunning golden autumn color all at once. One day it’s the usual green, then the next day – pow – it’s golden! And then a week later – boom – it’s naked! Seemingly, all at once! This is a no-nonsense plant that seems to want to make the change fast and get on with winter.
Our Cornus florida, Eastern Dogwood, changes color slowly and with a very different schedule, one that shows no particular pattern. Leaves along a branch that are bright red are interspersed with green or brown foliage or leaves just entering color change; some leaves drop much earlier than their companions showing the same amount of color change, some showing no signs of color change at all. It’s a pretty little tree but looks messy once chlorophyll starts to break down and its leaves begin senescence.
We walked past a stand of maples showing color change in the outermost leaves first; many leaves near the trunk still green, but the red of the changed leaves glittered and sparkled. Lovely!
Against a dark house, yellow/orange leaves of an old, leggy forsythia glowed sharp and bright in pale, gentle sunlight. This tall shrub’s autumn display tends to look like an after-thought; a haphazard and disorganized arrangement of changed leaves that persist on the plant while green leaves drop before any hint of change. Its ungainly growth habit doesn’t help, either. Odd how each plant responds differently to the same seasonal influences and internal processes. Odd, but beautiful.
I don’t know why one plants’ leaves change color from inside the canopy out, while another’s change from the outside in. Is it a result of a group of leaves having more of one type of chlorophyll than the other – more A than B for instance? All leaves contain both types of chlorophyll – A and B – and there is just a slight difference between the two in their molecular composition. Where A may not be able to absorb enough sunlight at a certain wavelength, chlorophyll B picks up the slack, thereby ensuring that the leaf absorbs enough light from the combined sources. Could it be that some leaves have received less water during the growing season than other leaves just a short distance away but on the same branch, thereby stressing those particular leaves? Could it be a slight variation in age of a leaf; one leaf opened earlier than a nearby leaf? Or could shade – either from within the canopy or an outside source – cause the discrepancy? I don’t know, and to date, I haven’t found an answer.
But, I do know the variety is delightful and I appreciate the show in all its diversity. And it’s a mystery I will continue to pursue.