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Science of the Season

This article first appeared in the 11/22/19 edition of the Davis Enterprise.

Science of the Season

Fall Maple Leaves. Photos by Dave Lauretti from Birlington, Canada.

Science of the Season


By Sara Thompson

Special to the Enterprise



Leaves changing colors and falling from trees is one of the most beautiful parts of autumn.  But how and why does this change happen?  And why are there other trees that do not shed their foliage?


During spring and summer time, the leaves of trees are absorbing sunlight and using it to make food for the tree.  This is the time that a tree will use this food and energy for new growth and to produce seeds, fruits, or flowers for pollination and reproduction.  The leaves are primarily green because they contain a chemical known as chlorophyll, which is essential for a leaf to convert sunlight into energy for the tree.  As temperatures cool and sunlight hours reduce, the chlorophyll in the leaves begins to breakdown, which in turn, allows the orange and yellow pigments in the leaf to show through.  The tree branches will also begin to sever the leaf attachment and create a “scab”, which will cause the leaf to break off and drop.  While the leaves are gone, trees go into a dormant period, where they are not growing but instead using nutrients stored in their trunk and roots to survive the colder months.


Not every tree will become bare during the colder parts of the year.  Most evergreen trees, or pines, keep their needles year-round.  The needles in pine trees are really just a modified leaf, rolled very tightly.  The tight shape, as well as a waxy coating, helps the needles retain water which helps them to continue photosynthesis during the wintertime.  These trees also do not use flowers to reproduce, but instead grow cones.  There are both male and female cones.  Male cones produce a pollen, and when fertilized, the cells in the female cones will become seeds for future trees.


These two types of trees have their own family names.  Trees that produce the large leaves that change color and fall to the ground are known as Deciduous trees, with the cone bearing pines being called Coniferous.  As with most things in nature, there are some exceptions to these rules, but this is a good general basis for the two tree families.  Mace Ranch Park has both of these types of trees side by side, check them out during a visit to our Science Center.



Explorit's coming events:



  • There are still opening for our Fall Workshops on November 25 & 26 from 9am-12pm.  Call (530) 756-0191 to register your child in grades K-6.


  • Explorit’s Nature Bowl team is still enrolling for the school year.  This is an afterschool science team from students grades 3-6.  Call (530) 756-0191 to register.  The $25 fee covers weekly meetings and a t-shirt.


  • It’s not too early to think about the holidays.  A great gift would be an Explorit Membership for your friends and family.  For more information or to purchase visit or call Explorit at 530-756-0191.  Purchase soon as membership prices increase January 1, 2020.



  • Giving Tuesday is December 3.  Support science education in your community by giving to Explorit.  We will receive matched funds from any gifts given on Facebook, check out more here
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