Plant Particulars October 2012

This year has been a fantastic year for fall color. Fall color is often best when the nights are cool with no frost and the days are dry, warm and sunny with little rain or wind to knock off the leaves. This is particularly true if the dry, sunny fall is preceded by an ideal, moist summer, which we did not have this year. Freezing temperatures will halt the mechanisms that create fall color, and the first frost of the season often marks the beginning of the end for fall color.

The shorter days and longer nights of fall are the primary trigger for trees and shrubs to produce fall color. This happens when the cells near the base of the leaf where it attaches to the branch begin to divide but not expand. This forms a corky layer of cells called the abscission layer that blocks the transport of water and nutrients to the leaves.

The colors you see in the many deciduous trees and shrubs come from two sources. The yellow and orange pigments come from xanthophylls and carotenoids. These pigments are always present in the leaves but masked by green chlorophyll. When the connection between the leaf and branch is severed, the chlorophyll dies, revealing these colors. The red and purple pigments come from anthocyanins which are created from the sugars that are trapped in the leaf when the connection of the leaf to the branch is blocked by the corky cells that form there each fall.

At Reiman Gardens, we have many great plants with some spectacular fall color, especially in the Hardwood Forest and Town & Country Garden. Stop out and enjoy the colors of the season!

Prepared by Aaron Steil, Education Coordinator