Science At Play: Preserving Fall Leaves

Did you find some beautiful leaves in your backyard this fall? Normally, leaves do not last forever, after a while they begin to grow bacteria or fungi. What if we told you there are ways you can easily preserve those leaves at home so you can save them for years to come! Pretty amazing, right!? Today, we are going to show you three different ways you can preserve your favorite leaves or flowers. Let’s get started!

Materials to Collect

• Fresh fall leaves (nothing too crispy or curled)
• Wax paper
• Iron
• Ironing board
• Thin towels
• Heavy books
• Newspapers
• Glycerin
• 2 styrofoam plates
• Small rock
• Paper towels
  

A note on collecting leaves:

Make sure to only collect from trees or plants that you know! Please do not collect leaves from poison ivy or poison sumac plants – while they turn beautiful colors in the fall, you may end up with an itchy rash! Also make sure you don’t pick leaves from any endangered plants or in state parks – we don’t want to harm our native wildlife!

If you want to keep the leaves fresh before starting the activity, you can put the stems in a jar of water so that they don’t get dried and crispy while you collect all the materials.

Try it!

Book Press:

1. Arrange your leaves on a piece of newspaper or paper towel, cover it with another piece of newspaper or paper towel.
2. Sandwich your pieces of newspaper in between heavy books – make sure to stack a lot of books on top for added weight.
3. Wait around 2 weeks until the leaves have dried. If pressing thicker leaves or flowers, make sure to change out the paper towels or newspaper every few days to get some of the moisture out of there.

Glycerin:

1. Make a mixture that is 1 part glycerin to 2 parts water (I used 1 cup glycerin to 2 cups water).
2. Pour some of the mixture onto a styrofoam plate.
3. Sink your fall leaves into the glycerin mixture and cover with the other plate. Place a rock or small weight on top of the plate to hold the leaves under the glycerin mixture.
4. Wait 3-6 days, then remove the leaves and pat them dry with paper towels.

Wax Paper:

1. Take your fresh fall leaves and place them in a single layer between two pieces of wax paper (wax side facing in if it is only coated on one side).
2. Place your wax paper – sandwiched leaves on a towel on your ironing board, and put another thin towel or paper towel over it.
3. Ask for an adult’s help to gently iron the thin towel covering the leaves on low or medium heat. Slowly move the iron in one direction until the leaf is sealed into the wax paper and the wax paper becomes slightly more see-through. It should take 3-5 minutes per side to seal the wax.

What is the Science? 

Pressing leaves and ironing them in wax paper work by removing water from the leaves. Without water, bacteria and fungi can’t grow and make the leaves rot like they would outside or in a compost heap. Glycerin is a natural preservative that is used to keep some foods, cosmetics, and scientific collections fresh by retaining moisture.

With the book press, the pressure from the weight of the books helps press and flatten the leaves as the newspaper absorbs the water from the leaves. This method is similar to what plant scientists, or botanists, use to preserve leaves for their collections – they make a leaf press out of layers of cardboard and newspaper between two wooden boards that is squashed by tightening screws or straps. This allows the collectors to arrange the plants before pressing, and preserving them by drying them quickly – before mold can destroy the leaves. This method also stops the leaves from curling up as they dry like they do outside, this way they keep their shape! 

A collection of dried leaves is called an herbarium – you can make your own herbarium at home by gluing your dried, pressed leaves onto paper and labelling them with what plant it is, where you found it, and when you collected it! Scientists use herbariums to study how plants change over time, and what plants grew in different areas at different times. You can check out the New York Botanical Garden’s C.V. Starr Virtual Herbarium – a digital collection of high resolution photographs of the plants contained in the herbarium so that researchers around the world can view these plants!

The glycerin method works as the leaves slowly absorb the glycerin, it replaces some of the water within the leaf. Glycerin is used to preserve specimens in biological collections and to preserve food and cosmetics. Once you soak the leaf in the glycerin mixture, the leaf becomes filled with a mixture of glycerin and water – since glycerin is a liquid, your leaf will remain flexible like a fresh leaf!

Finally, with the wax paper method, the heat from the iron is evaporating some of the water out of the leaves, while the wax protects the leaf from any new water or bacteria entering and rotting the leaf.

 Ask Your Young Scientists

• What does the leaf look like once it has been pressed, soaked in glycerin, or ironed in wax paper? How do the leaves feel?
• How are they different compared to a leaf that has been left out to dry on the counter/outside?

More to Explore

Try a few ways of preserving leaves, see which ones hold their color or last the longest!

Science At Play: Leaf Chromatography – learn more about the pigments in fall leaves and reveal the pigments with this hands-on experiment

SciShow: Why Do Leaves Change Colors and Fall?
SciShow Kids: Why Do Leaves Change Color in the Fall?

This content was made possible in part by the Institute of Museum and Library Services.

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