In Da Woods
by Melanie B. Fullman, US Forest Service
Falling in Love
Walking through the woods these days is amazing! The
colors, the smell of the leaves, the crispness of the
Brilliant Survival Technique
Perennial plants, including trees, must have some sort
of protection to survive freezing temperatures and other
harsh winter conditions. Stems, twigs, and buds are
equipped to survive extreme cold but tender leaf tissues
are not, so plants must either protect their leaves or
dispose of them.
Conifers, such as pines, spruces, cedars, and firs
evolved with built-in protection. Their needle-like or
scale-like foliage is covered with a heavy wax and the
fluid inside their cells contains substances that resist
freezing. Thus, the foliage of evergreens can safely
withstand all but the severest winter conditions, such
as those in the Arctic.
The leaves of broadleaved plants, on the other hand, are
tender and vulnerable. These leaves are typically broad
and thin, unprotected by any thick coverings. The fluid
in their cells is a thin, watery sap that readily
freezes. This means that the cells cannot survive
temperatures below freezing. Tissues unable to
overwinter must be sealed off and shed to ensure the
plant's continued survival.
In response to the shortening days and declining
intensity of sunlight, leaves begin the process that
eventually leads to their own ‘downfall’. As the veins
that carry fluids in and out of each leaf gradually
close, a layer of separation cells forms at the base of
each. Once this layer is complete, the connecting
tissues are sealed off, and the leaf can no longer stay
attached to the tree. But before that happens…
Three factors influence autumn leaf color: leaf
pigments, length of night, and weather. The timing of
the color change and leaf fall is primarily regulated by
the increasing length of night/shortness of the days.
None of the other environmental influences –
temperature, rainfall, food supply, etc. – are as
unvarying as the steadily decreasing daylight. As the
nights grow longer and cooler, biochemical processes in
leaves begin to paint the landscape.
The amount and brilliance of the colors that develop in
any particular autumn are related to weather
conditions. The temperature and moisture that occur
before and during the time the chlorophyll is dwindling
are the main influences. The countless combinations of
these two highly variable factors assure that no two
autumns are exactly alike. A warm wet spring, favorable
summer weather, and warm sunny fall days with cool
nights usually produce the most brilliant autumn colors.
A late spring or severe summer drought can delay the
onset of fall color by weeks, and a warm fall often
lowers the overall intensity of the colors.
During the growing season, chlorophyll is continually
produced so leaves constantly appear green. As night
length increases in the fall, chlorophyll production
slows down and eventually stops; there is just not
enough light or water for photosynthesis during the
As each tree shuts down its photosynthesis factory, its
green chlorophyll disappears. Other pigments in other
shades suddenly become visible. They were there all
along but unmasked by the lessening green-ness, the
“new” colors can be spectacular.
RED & PURPLE anthocyanins are common in fruits such as
cranberries, apples, concord grapes, blueberries,
cherries, strawberries, and plums. They are water
soluble and in trees, exist primarily in the watery
liquid of leaf cells. Warm, sunny days and cool, crisp,
but not freezing nights makes trees produce lots of
sugars. But as the leaf veins close, the sugars are
prevented from moving into the tree’s truck and roots.
In the fall, trapped sugars tend to contain an abundance
of anthocyanin pigments. The result is leaves in
brilliant shades of red, purple, and crimson.
YELLOW, ORANGE, & BROWN colors are the result of
carotenoids, which also occur in and provide
characteristic coloring to corn, carrots, daffodils,
rutabagas, buttercups, and bananas. Because carotenoids
are always present in leaves, yellow and gold hues
remain fairly constant from year to year, whereas reds
and purples tend to vary.
In addition, certain colors tend to be attributable to
certain species of trees. Oaks generally turn red,
brown, or russet; aspen a golden yellow; and dogwood,
purplish red. Red maple tends to be a bright scarlet;
sugar maple, orange-red; and black maple, glowing
yellow. Leaves of some species, such as elms, simply
shrivel up and fall off, exhibiting little color other
than drab brown.
The timing of the color change also varies by species.
Oaks put on their colors long after other species have
already shed. Such differences seem to be genetically
inherited, for a particular species at the same latitude
will show the same coloration at high elevations as it
does in warmer lowlands.
Coloring in the Lines
Of course, you don’t really have to know a thing about
carotenoids and anthocyanids to enjoy the peak of fall
color, happening right now. Take a friend, a
camera, and walk down just about any lane or street in
the western UP or northern Wisconsin. Just go outside
and relish autumn in the North Woods.
PS: don’t forget the FREE fall color tour (hike and
Copper Peak ride) this Saturday, Oct. 1. Contact Jason
Hofstede at 932-0845 to register or for more
See YOU in the Woods.
View More Photos by Bob Severin
to everyone who submitted
recipes for the Polar Bear
Hockey Cookbook. The cookbooks
are now available. The cost for
the cookbooks are $10.00 so make
sure to grab one for yourself
and maybe one or two as a gift.
They can be purchased at the Pat
O'Donnel Civic Center concession
stand or by contacting Kerry
Roehm or Micki Sorensen.