Science ideas for young children: Part 13 – Falling leaves

Teach young children about science by enjoying fall leaves.

This is the 13th article in a series by Michigan State University Extension about science activities that can be done in the natural world that anyone can conduct with children.  This can be done within a family, in a day-care setting, as part of school activities, a 4-H club or with any group working with young children. 

Kids love to ask questions and try to figure things out is a great way to learn science.  Fall is a great time to learn about science as many things that happen and change during this time.  Here are some questions, answers and experiments to do with falling leaves.

  • Why do leaves drop in the fall?
    • Let the young people come up with ideas and see how they can test it.  If they think it is because of colder weather, let them put a tree branch in water and then refrigerate it to see if the leaves fall off easily.
    • If they think it is because of shorter days, experiment by taking a small potted tree and putting in a closet where you have the light set on a timer.  Make a shorter “day” and see if the tree loses its leaves (shorter days means less photosynthesis occurring).
  • How does it benefit trees to drop their leaves?
    • The purpose of leaves is to turn sunlight, carbon dioxide and water into food for plants so the plant can get bigger and produce more seeds.
    • In the winter, days are shorter, so there are fewer daytime hours and less time to make food.
    • When leaves are making food, they draw water up from the roots through tubes called xylem.  If that water is trapped and freezes in the xylem when the weather gets cold, the “pipes” could burst, killing the tree. 
  • Why do some leaves drop sooner than others?
    • Ask the children to notice which trees lose their leaves first.  Are there any patterns?  Is it trees of a certain kind (same leaf shape)?  Is it trees that are in a certain area?  Are there things that might be blocking the wind, sun or rainfall that could lead to the changes?
    • There are many reasons why trees lose their leaves at different times.  Have the children make a guess about why and see if they can find evidence to back it up.  If they think it is a certain type of tree, they can look at trees in other places in your neighborhood.  If they think it is that they are near a road, look at other trees near the road and see if those are the same.  Look for signs of insect, wind or lawn mower damage on the tree.
  • Why don’t pine trees (sic) lose their needles?
    • All trees with needles aren’t pine trees, the proper term is conifers.  They might be pines, spruces, cedars or other trees.  A guide is available online to help identify these tree types.
    • Broad leaves lose a lot of water.  Whipping winter winds make that problem even worse.  If you cut a small branch off both a conifer and a broadleaf tree and put them in two separate vases, then blow a fan over the branches, the water from the broadleaf plant should evaporate faster than from the conifer.
  • Why do leaves change color?
    • There are pigments in leaves that turn sunlight, carbon dioxide and water into food for the plant.  The most common one is chlorophyll, which is green.  In the fall plants produce less chlorophyll, which allows the other pigments (which are there all along) to be seen.
    • Do some trees have different colors? Do trees in different areas turn color sooner?

Encourage the young people you work with to ask questions about falling leaves and build the scientist within themselves.

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