As the dog days of summer trot into autumn, you might start thinking about one of nature's most spectacular showsthe annual fall foliage display that can break out like brilliant slow-motion fireworks in woodlands around the country.
Let's face it though, not all fall leaf displays are created equal. While some autumns explode like the Fourth of July, others fizzle like a wet roman candle.
What Makes Some Year's Leaf Displays Better Than Others?
Actually, a few different processes work together to make an autumn leaf display.
As daylight shortens at the end of summer, a layer of cells grows at the base of each leaf stem, cutting off the water supply like a cork.
Along with other metabolic changes, this stops production of green chlorophyll in the leaf. When the chlorophyll breaks down, it unmasks yellow or orange pigments that have been present in the leaf all summer, but only now become visible.
Why Do Leaves Change Color?
For leaves that turn red or purplish, a different process occurs.
Reddish pigments are manufactured in the leaf as summer ends, created from sugars that are trapped in the leaf by that same cork-like growth of cells.
Cool late-summer nights work best for retaining these sugars in the leaves, and sunny late- summer days are best for converting the sugar to pigment.
Sunny Days And Cool Nights
Finally, some leaves like oaks have rich brownish pigments, due to tannins in the leaves.
Since the most spectacular autumn displays will combine all these colors, you'll want sunny days and cool nights in the late summer for the most spectacular natural fireworks in the fall.