Why Leaves Change
The key to Ohio’s vibrant autumn color season is a combination of long, cool nights and short, sunny days in mid to late September.
Decreased amounts of sunlight in the fall trigger a chemical change in the leaves of hickory, birch and beech trees which causes them to turn various shades of yellow, brown, and orange. These colors, called carotenoids, are present in the leaves all year long, but are hidden by green chlorophylls during the spring and summer.
Additional shades of red and purple, called anthocyanin pigment, develop in late summer in the sap cells of tree leaves that are rich in sugar, including maples, oaks, sweetgums, and dogwoods.
In woodlands, where there are trees rich in carotenoids and anthocyanins, the combination of fiery reds, golds, and bronzes can light up a vista, creating the typical autumn landscape so familiar to Ohioans. With more than 100 species of trees in the state, it is no wonder Ohio’s Fall Color season is so spectacular.
What makes the leaves fall from the trees? As fall approaches, the sap starts to thicken and slows its flow. This protects the tree from freezing over the winter. When this occurs, thickened sap clogs the leaf veins. The leaves then become saturated with sugar created by the chlorophyll. During this process the union between the branch and leaf seals off and the weight of the leaf, in combination with wind and rainstorms, eventually causing it to fall.
Which Tree Species
Turn Which Colors In The Fall?
While many of Ohio's hardwood (deciduous) trees can be divided into two color groups - reds and yellows - others reflect both colors as well as varying shades of orange, purple and dark russets. Here are a few of Ohio's more common trees and the colors you can expect to see on their leaves.