The colors of fall are busting out on trees and shrubs across Pennsylvania as the chemistry in their leaves makes the annual autumnal shift.
Spring through summer high levels of green chlorophyll have held sway in the leave.
But as temperatures and daylight have grown less, production of chlorophyll has declined.
That has cleared the way for other compounds, already present in leaves but overshadowed by the abundant chlorophyll, to make their presence known.
Flavonoid compounds in the leaves are responsible for the yellows. Carotenoids produce the orange-reds.
Anthocyanins, a type of flavonoid, gives us the deep reds, purples and magentas. Unlike the other flavonoids and the carotenoids, anthocyanins are not present in the leaves until fall. They are produced when diminishing chlorophyll clears the way for sunlight to interact with increased concentrations of sugar in the leaves.
Here’s how all that chemistry plays out in the fall foliage you’re seeing now in some of the more common trees and shrubs across Pennsylvania.
- Golden-yellow – American elm, black cherry, cucumber magnolia, hop hornbeam, quaking aspen, shagbark hickory, striped maple, sugar maple, tulip poplar and witch hazel.
- Yellow – beech, bigtooth aspen, chestnut, mountain ash, mulberry, paper birch, pawpaw, pignut hickory, redbud, river birch, slippery elm, spicebush, sugar maple, sweet birch and white oak.
- Pale yellow – bittersweet, black walnut, green ash and sycamore.
- Bronze – beech, box elder, chestnut oak and white oak.
- Orange – fire cherry, ironwood, gray birch, poison sumac, red maple, sassafras and sugar maple.
- Red – black gum, mountain ash, poison sumac, red maple, red oak, sassafras, white oak and sugar maple.
- Scarlet – scarlet oak, smooth sumac and staghorn sumac.
- Maroon – flowering dogwood, gray dogwood and white oak.
— Marcus Schneck, PennLive