2007 Year in Review

Browning Evergreen Foliage

Every fall, some people become upset when the foliage on their evergreens changes color dramatically, said a University of Illinois Extension horticulture educator.

"People are convinced that their plants must have some type of virus or fungus and want to know what can be done," said Martha Smith. "There is really nothing to be concerned about. What is happening is commonly called inner needle drop or third-year needle drop."

All trees and shrubs renew their foliage annually, producing new leaves in the spring of the year and shedding old leaves in the fall, she explained. The leaves of deciduous plants such as maples and oaks live for one growing season and then fall off, usually in a blaze of color.

"But evergreen foliage lives from one to several years, depending on the species," she said. "As new growth emerges in the spring, last year's growth becomes shaded. Its role as primary photosynthesizer is over. During late September and October, this inner or older foliage dies and falls away."

In some species like white pine and arborvitae, this fall browning takes place rather suddenly. The older needles turn a bright gold-yellow and remain attached for about seven to 10 days, depending on weather.

"If we have strong autumn winds and heavy rains, those needles fall quickly," Smith said. "Sometimes, this natural occurrence is hardly noticed. But every few years it is very noticeable, and people become concerned."

This natural foliage drop may be distinguished from cases of severe foliage damage due to disease by its uniform appearance over the whole tree and its common occurrence on neighboring trees of the same kind. It is also confined to the innermost or oldest needles. Nearly all pines bear needles in bundles of two or five, and the needles remain together when they drop.

"No harm is done to the tree by the loss of this foliage," she said. "The amount dropped depends somewhat on the condition of the tree and the preceding growing seasons. Less vigorous individuals will lose a greater proportion of their total leaf area. If the new, terminal, or current year's growth is fresh and vigorous, the health of the tree is not in jeopardy."

by  Editor, theCity1.com
September 27, 2007