Enjoy the beauty and science behind the fall colors – The Ukiah Daily Journal

The brilliant fall color in our landscapes is a magical transformation that happens every year. And the science behind it is just as intriguing.

Each fall, as the days grow shorter, our deciduous trees and shrubs begin this transformation. Plants produce less chlorophyll which gives leaves their normal green color. The existing chlorophyll begins to break down, revealing the underlying yellow, red or orange pigments.

Carotenoid and xanthophyll pigments help chlorophyll to capture light and produce sugar during the growing season. Beta-carotene contributes to the orange and yellow-orange fall color. Lutein is the most important xanthophyll pigment producing a bright yellow fall color. There are over 80 different pigments in these two categories that contribute to fall color variations.

The tannins of the leaves contribute to the golden and brown fall colors. These are believed to discourage animals and pests from feeding on the leaves and help defend plants against pathogens.

At the same time, these plants begin to create an abscission layer between the leaf and the stem. This barrier prevents the sugars produced in the leaves from descending into the roots for storage.

The purple and red fall color, from the anthocyanin leaf pigments, is produced when sugars accumulate and become trapped in the leaves. This results in a brilliant red and purplish red fall color. Some of these pigments are present during the growing season and can be seen in new shoots and mature leaves of some plants. These add color to the garden, help protect plant cells from light damage, and can discourage animals and insects from eating on plants.

Warm, sunny days followed by cool nights without a hard frost mean more sugar and a better red, orange and purple fall color. Sufficient soil moisture helps keep leaf color shiny for a longer time. The leaf color fades, turns brown, and leaves fall off the tree more quickly in dry fall weather.

Fall foliage isn’t limited to deciduous trees and shrubs. The leaves of many of our favorite perennials also take on vibrant colors in the fall.

Solomon’s seal and hosta leaves turn a beautiful yellow, echoing the fall flowers of witch hazel and yellow leaves of ginkgo and trembling aspen. The delicate heart-shaped leaves of the tundra, known botanically as Epimedium, turn red in the fall. Some leaves fall in the fall like most trees and shrubs. Others will persist throughout the winter and drop off as new leaves and flowers appear in the spring.

The leaves of perennial geranium and bergenia turn red-purple in the fall. Both will persist, adding color to the winter garden and early spring.

Brighten up the fall landscape with the fine texture and amber-gold fall foliage of Angelina sedum and amsonia willow.

The fluffy white seed heads of our little native barbon complement the coppery red fall color that persists all winter.

Genetics determine the color that each plant tends to produce in the fall, while weather and plant health influence whether and how intensely the color will be expressed. Consider the color of fall when adding plants to the landscape. Then proceed with proper care to keep them healthy and in their best shape throughout the year.

Melinda Myers is the author of over 20 gardening books, including The Midwest Gardener’s Handbook and Small Space Gardening. She hosts The Great Courses ‘How to Grow Anything’ DVD series and Melinda’s Garden Moment television and radio program. Myers is a columnist and editor for Birds & Blooms magazine. Her website is www.MelindaMyers.com.

Each fall, as the days grow shorter, shrubs and deciduous trees like this Korean maple to arctic jade begin their transformation as plants produce less chlorophyll. (Photo provided)


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Terri S. Tomasini