Look closerPlants
Why leaves change color in fall: the yellows were there all along
When: September to October
The yellows and oranges of a Massachusetts fall sit hidden in the leaves all summer, unmasked when shortening days shut down the green chlorophyll that covers them.
Why this time of year
First color reaches eastern Massachusetts by mid-to-late September, led by red maples, while late changers like the oaks hold out until mid-to-late October.
How to notice it
- Find one tree just starting to turn and study a single leaf that is part green, part yellow.
- Compare early movers like red maple with still-green oaks on the same street.
- Watch one tree across two weeks: does one side turn first?
- Sort fallen leaves into a line from yellow through orange to deep red.
Try this with kids: Can one tree show three different stages of color at once?
carotenoids are the yellow and orange pigments present in the leaf all season
Sources
- fs.usda.govAs night length increases in autumn, chlorophyll production slows and is eventually destroyed, and the carotenoids and anthocyanin present in the leaf are unmasked and show their colors
- massaudubon.orgMassachusetts timing: early foliage changes can happen mid-to-late September, red maple among the first to turn, and oaks and aspens change mid-to-late October
In the guide for September, October