The Science of Fall (with Activities)

Autumn brings the cool weather which can be sad for some who love the summer weather, but there’s something else that comes along that many still marvel at in this season. Autumn is when we start to notice the leaves. They are everywhere! They are on the trees and falling into our yards and into the streets around us. They are also great material for science activities. Let’s take a closer look at the importance of leaves.

Why Are Leaves Important?

The leaves are the food source of the tree. Through a process called photosynthesis, the leaves work throughout spring and summer to use the water and sunlight it receives each day to produce nutrients or sugar for the plant to grow and flourish. It takes in carbon dioxide and releases oxygen through this process as well. 

Why Do Leaves Fall?

When autumn arrives, the trees begin to prepare for the winter. It starts absorbing all the nutrients. As the leaves begin to lose their nutrients, their colours begin to change. Eventually when there is nothing left, they start to fall or get blown away by the autumn breezes. This is why autumn is also called “fall.” It’s interesting to note that this process of absorbing the nutrients from the leaves on the tree makes the leaves recyclable when they fall to the ground, becoming nutrients for the soil. 

Parts of a Leaf

While a leaf may be a small part of a very large tree, each leaf has its own intricate design to fulfill its purpose in the plant life cycle. 

A leaf is composed of

• The Blade - The broad flat part of the leaf is called its blade or lamina. The functions of the blade or lamina include preparing the food for the plant using the water, minerals, and carbon dioxide through photosynthesis. The blade is made up of three parts.
  • The apex - the tip of the leaf
  • The margin - the edge of the leaf
  • The veins - small channels or capillaries that run through the blade.

• The Petiole - This is the stalk of the leaf. This is the part that connects the leaf to the plant and helps to keep it erect. It is made up of vascular tissues that transport food and water through the process of photosynthesis. 

Why Do They Change Colour?

Leaves have a chemical called chlorophyll that helps produce the food and water that the plant receives and gives the leaves their green colour. In the fall, the leaves stop producing chlorophyll, store the nutrients left in the leaf in its roots, and the green colour begins to change. With the chlorophyll gone, there are other chemicals left behind like carotenoids. (This is what gives carrots their orange colour.) Some leaves turn orange and others, which have different chemicals, will turn their leaves to yellow or red.

Leaf Science Activities

Here are some application activities for you to try.

Young Children - Leaf Collage

Head on outside and start collecting leaves. Try to get some really nice ones that haven’t been crushed yet. Once you’re back inside, grab some cardstock or construction paper and some glue and start making a fall collage with your leaves. You can even put your collage in a frame once you’re done and hang it in your room for some beautiful fall decorations!

Middle-aged Children - Leaves By Colour

Get outside and grab as many different coloured leaves you can and bring them back inside. Begin to sort your colours. Once you’ve got your leaves organized by colour, create a graph and place your leaves in their colour category.

Here is an example of what your graph could look like.

Bonus - Can you tell which tree the leaves came from? Write the names of the trees down underneath your leaves. 

Older Children - Leaf Rubbings

Materials needed:

• A leaf (or two for backup)
• Paper - You can choose from the following options.
  • Tracing paper
  • Wax paper
  • Parchment paper
• Crayons or coloured pencils

Instructions:

1. Head outside and grab a nice big leaf that is still intact and not crushed. 
2. Place your leaf upside down and place your paper over the top on a flat surface.
3. Choose your colour. (Darker colours will give you better results.)
4. Carefully hold your paper as you press your crayon or pencil over the top and colour over the top of your leaf until you begin to see the outline. 
5. Try to get as close to the margin printed out on your rubbing.
6. Once you are finished, see if you can label the parts of the leaf.

For fun: Make a collage of leaf rubbings to hang in your room!

Be inspired with this short video about making leaf rubbing art.