Woody plants for autumn color

By Dawn Pettinelli - UConn Home & Garden Education Center
Featured Article - posted Wed., Sep. 26, 2012
- Contributed Photo

We are indeed fortunate living in New England, which is among the few parts of the country where one can experience the marvelous colors of autumn. This is due to both the abundance of deciduous trees and our particular climatic situation.

Fall color varies from year to year. Because of this past summer’s heat and drought, many plants have been stressed, and a less than spectacular but none-the-less satisfying fall foliage season is expected.

We all know that leaves are the color green because of the chlorophyll they contain. With the cooler autumn temperatures, less chlorophyll is produced, and what remains in the leaf disintegrates. Plants with leaves containing the pigments carotin and xanthophyll turn yellow as the amount of chlorophyll decreases.

The red color in leaves is caused by the pigment anthocyanin, and is a result of sugar and tannin accumulations in the leaf. Unlike the leaves that turn yellow in the fall, red-colored foliage can vary considerably in its brilliance depending on the weather. Especially bright reds occur during autumns with bright, warm, sunny days followed by cool nights. The sugars get trapped in the leaves, as no translocation can take place. On the other hand, falls with many cool, cloudy days exhibit less intense leaf color.

Often you will notice a tree where only parts or perhaps one side turns red. These places on the tree are generally exposed to the most sun. Plants located in low-lying areas such as wetlands have a tendency to color earlier because cold air will collect in these sites.

Be on the lookout, however, for plants in the landscape that change their leaf color prematurely. This often indicates the plant is under stress because of past winter injury, summer drought, unmet cultural requirements, physical injury, disease or insects.

A plant’s condition not only affects the time of leaf change, but also the color. A tree or shrub receiving adequate water and nutrients will produce a more spectacular color display than one that does not. Also, it should be mentioned that some trees or shrubs, by nature, are really quite nondescript in their fall wardrobes, merely changing from green to brown. It is thought that either the chlorophyll breakdown is not complete or it occurs too late in the season.

When selecting new trees and shrubs for your yard, think about their autumn coloration along with your other requirements.

Woody plants with yellow leaves in the fall include birches, shadbush, eastern redbud, yellowwood, clethra, gingko, witch hazel and larch.

Some of the best reds can be found in red and sugar maples, American hornbeam, flowering dogwood, cornelian cherry dogwood, fothergilla, tupelo, sourwood, sassafras and some viburnums and azaleas. Enkianthus turns an almost iridescent reddish orange.

Purplish overtones show up in grey dogwood, white ash, leucothoe, mahonia and some junipers.

Enjoy the colors of autumn now, for winter is just around the bend. If you need help selecting plants with good fall color or have other gardening questions, call the UConn Home & Garden Education Center (toll-free) at 877-486-6271, visit www.ladybug.uconn.edu, or get in touch with your local Cooperative Extension Center.

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