Autumn
Activities & Crafts
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Why
Do Leaves Turn Colors in the Fall?
by
Don Janssen, Extension Educator
Folk
tales about the cause of fall leaf colors are entertaining, but
the scientific explanation is almost as interesting. Autumn leaf
colors are the result of a chemical change in the leaves. The
trigger is the onset of cooler temperatures and reduction in day
length.
During
the growing season, green leaves are green because of the large
amounts of chlorophyll they contain. Chlorophyll is the key component
in photosynthesis, the process by which leaves use sunlight and
carbon dioxide to make the sugars and starches the tree uses for
food. As long as they are growing, trees continually replenish
their leaves' supply of chlorophyll. As the days get shorter and
cooler, however, growth slows and the tree produces less chlorophyll.
As chlorophyll in the leaves breaks down, it isn't replaced, and
the other pigments that have been there all along, masked by the
green, become apparent.
The
yellows, oranges and browns commonly seen in birch, hickory, aspen
and some maples come from a group of pigments called carotenoids.
These are the same pigments responsible for the colors in carrots,
bananas and field corn.
Red
and purple coloration in leaves of trees such as oak, sweetgum,
dogwood and some maples is caused by anthocyanins, the same pigments
that color cherries, grapes, blueberries and apples. In trees
with green leaves, carotenoids are present in leaves all summer,
but anthocyanins are produced in late summer and early fall in
response to environmental cues.
Both
kinds can occur in the same leaves and can combine to produce
the fiery reds, oranges and bronzes seen in dogwoods, sumacs,
oaks and maples. A wide range of colors is possible, though the
basic color varies from species to species and cultivar to cultivar.
The
intensity of color varies from year to year, depending on the
weather. The conditions most favorable for brilliant reds are
bright, sunny, warm days and cool nights. The leaves produce more
sugar on warm days, and night temperatures below 45 degrees keep
those sugars in the leaves. Pigments are formed in those sugars,
so the more sugars, the more color.
When
night temperatures are warm, the sugars exit the leaves and colors
are less intense. Cloudy, wet weather that interferes with sugar
production also tends to dull the fall color display. And an early
hard frost that kills leaf tissue will result in a predominance
of brown.
Fall
color that occurs out of season means trees are stressed from
drought, insect attack, low soil fertility, a girdling root or
some other problem.
Rake
Up
Age: 4 and Up
Mess: Low
Material:
Rakes and bags
Instructions: Have your child help rake up your
leaves. I found a big difference between my youngest when she
was four and helped me instead of three. We had a lot of fun together
and afterwards we had a nice hot cup of Hot Chocolate.
Leaf
Prints
Age: 4 and Up
Mess: Medium
Material:
Leaves, construction paper, non toxic paint and a paint brush
Instructions: Collect leaves from your backyard
and glue the leaves onto a sheet of cardboard. Allow them to dry
completely. Pour a small amount of paint onto a plate and use
a paintbrush and paint the leaves different colors. Lay a piece
of green or black construction paper over the painted leaves and
rub back and forth over the paper with your hand. Lift the paper
to see your leaf print!
Aluminum
Foil Leaves
Age: 4 and Up
Mess: Medium
Material:
Pieces of aluminum foil, leaves, glue, scissors and construction
paper
Instructions: Set pieces of aluminum foil and
a variety of fall leaves in front of your child. Let them select
different leaves and place each of them under a piece of foil.
Gently press and rub the foil with their hand to get a leaf print.
Then cut the shape and glue their leaf prints to the construction
paper.
Squirrel Hunt
Age:
3 and Up
Mess: Low
Material:
Mixed nuts
Instructions: Hide the nuts throughout
a room and let you child pretend to be a squirrel and gather the
nuts by tasting the nuts that have been discovered.
Leaf Necklace
Age:
4 and Up
Mess: Medium
Material:
Colored construction paper, crayons or markers, scissors, hole
punch, and yarn
Instructions: Draw some leaf shapes on
different colored paper and help your child cut them out. Have
your child decorate them with the markers or crayons. Punch a
hole in the leaves and give your child some yarn, and have them
thread them on to make a necklace.
Dry Leaves
Age:
4 and Up
Mess: Medium
Material:
Green construction paper, dry fall leaves, glue and brushes
Instructions: Cut a fairly large leaf
shape from construction paper. Have your child brush glue on their
leaf shapes. Then let them crinkle dry leaves and scatter the
pieces all over the glue.
Real
Trees
Age:
4 and Up
Mess: Medium
Material:
Green construction paper, dry fall leaves, glue and brushes
Instructions: On the sheet of paper draw
a tree with no leaves. Cover it with glue and then sprinkle crumpled
up dried leaves to fill the branches.
Water
Leaf Prints
Age:
4 and Up
Mess: Low
Material:
Warm fall day, paintbrush, bucket and water
Instructions: Have you child paint some
fall leaves with water, then press them on the driveway or sidewalk.
See the patterns the print makes. Talk with your child about what
the veins in the leafs do that make the shape designs.
Collect
and Sort
Age:
4 and Up
Mess: Low
Material:
different fall leaves
Instructions: Have your child collect as many
leaves as they can find. Go back inside and have your child put
the leaves into groups of small, medium and large.
