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Every fall, people get upset when their evergreens
undergo dramatic changes
in color. “People are convinced that their plants must
have some type of virus or fungus and want to know what can be done,”
says Martha Smith, a horticulture educator with the University of Illinois
Extension. “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. The leaves of deciduous trees 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,” Smith says. “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, such as white pine and arborvitae,
this fall browning takes place rather suddenly. The older needles turn a
bright gold-yellow and remain attached for seven to 10 days, depending on
weather. “If we have strong autumn winds and heavy
rains, those needles fall quickly,” Smith says. “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 caused by disease by its uniform appearance
over the entire 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 says. “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.”
For information about the University of Illinois
Extension Sangamon-Menard Unit, go to www.extension.uiuc.edu/Sangamon.
This article appears in Sep 6-12, 2007.
