Every fall, questions arise concerning the foliage on evergreens changing color dramatically. Callers are convinced that their plants must have some type of virus or fungus and want to know what can be done. "There is really nothing to be concerned about," explains Martha Smith, Horticulture Educator, University of Illinois Extension. "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. 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. As new growth emerges in the spring, last years 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 7 to 10 days depending on weather. If we have strong autumn winds and heavy rains, these needles fall quickly. 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 to five, and the needles remain together when they drop.
No harm is done to the tree by the loss of this foliage. 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.
Pull date: November 20, 2012