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Today we are joining with Share It! Science News blog in a kid-friendly investigation of composting. Here at Growing With Science we have activities to explore decomposition and the organisms found in compost. Share It! Science News is delving deep into composting with earthworms (vermicomposting). Be sure to go over and see what earthworm eggs look like.

Compost Science

Spring is a perfect time to add last year's compost to the garden and start this year's compost heap. While you are at it, why not incorporate some science activities for children?

Activity 1. Exploring Decomposition

Decomposition is an incredibly important process. Things rotting and decaying may not be pretty, but imagine what the world would be like without decomposition. Dead organisms would pile up and the nutrients tied up in them would not be released to be used again.

Test to see whether the addition of soil speeds up decomposition.

Note:  The observation portion of this experiment will take two to four weeks depending on materials used, temperature, and humidity. Also, set up outdoors or in a well-ventilated area and warn children not to disturb, inhale, or eat decaying materials.


  • Clear containers, gallon-sized or bigger, if possible
  • Squares of fabric to cover container
  • Rubber bands to hold cloth covers in place
  • Plant debris, like leaves, grass clippings
  • Fruit and vegetable scraps, grains (no meat)
  • Soil, potting mix, or finished compost
  • Cup to measure soil and water
  • Water source
  • Optional:  man-made materials (to check if they are biodegradable)
  • Optional:  thermometer

Prepare two containers with identical mixes of plant material and the same amount of water (enough to make damp).


Add a cup of soil, potting mix, or finished compost to one container.

decomposition-experiment-2Observe the two containers daily and record which one seems to contain materials that are decomposing more quickly. If there is a thermometer available, record the temperature of the mix each day. Add water as needed (same amount to both containers). Compare and discuss your results when completed.

Note:  Too much water will cause anaerobic conditions or lack of oxygen. The microorganisms that grow under anaerobic conditions tend to smell really bad. If that happens and you want to try to save the experiment, pour off the excess water and stir in some dry leaves or grass clippings (same amount in each container).

Extension 1:  Prepare more containers to compare the effect of adding soil versus potting soil and/or finished compost.

Extension 2:  Add various man-made materials to test to see if they are biodegradable. Examples might be different types of packing peanuts, pieces of Styrofoam, pieces of plastic bags, cardboard, or different types of paper.

Activity 2. Discovering Critters in the Compost

A compost pile is a community of living things that are dependent on each other. Microorganisms such as bacteria, yeasts and molds are at the forefront of the decomposition process. Helping them (or eating them) are the invertebrates. The invertebrates help the microorganisms by tearing up or breaking up the larger pieces of plant material and by moving microorganisms about on their bodies. Remember that a compost pile that is working optimally will be too hot to harbor much besides microorganisms.

Compost.bin(Photograph of compost bin in public domain at Wikipedia)

Look through a sample of compost to see what critters are found hiding there.


  • Magnifying lens
  • Dissecting microscope, if available
  • Petri or specimen dish to hold sample
  • Tweezers, forceps or a small stick to poke through compost
  • Small paintbrush to remove debris and move tiny creatures
  • Paper and pencil to make drawings and record results
  • Gloves (optional)
  • Identification guides, or take a look at descriptions of compost critters

What invertebrates should you expect? (Links go to related Growing With Science posts)


beetles, crickets, cockroaches, ants, flies like fruit flies, silverfish, or earwigs

2011-antsCrickets, cockroaches, some flies, and some beetles feed on the plant materials added to compost. The ants, riparian earwigs and most beetles will be feeding on other creatures living in the compost pile or bin.

Snails, slugs

snail-2Slugs and snails may feed on leaves of plants added to a compost pile and help break up large pieces.





Public domain photograph by Alex Wild

All the arachnids feed on other animals (are predators).

Millipedes, centipedes


Millipedes feed on decaying plant materials. Centipedes are predators of other animals.



Earthworms help make big pieces of plant materials smaller. See Share It! Science News for how to compost with worms.

Sowbugs, Pillbugs


Sowbugs and pillbugs also feed on decaying plants.

Nematodes (round worms)

Nematodes are by far the most abundant invertebrate found in compost heaps. They are tiny hairlike worms usually visible only under the microscope. It has been estimated that a single rotting apple may contain as many as 90,000 nematodes!


  1. See our post with composting activities to accompany the Rotten Pumpkin Book
  2. Our post about decomposing tree leaves
  3. Compost Stew Book Author Website has loads of links to compost lessons, games, information, etc.
  4. Compost Stew lesson plan from Books in Bloom (download here)
  5. Resource for older children:  food web of the compost pile illustration (download here)

Try our growing list of children's books about decomposition and compost at Science Books for Kids.


Follow Roberta's board Compost Science for Kids on Pinterest.


Right in time for the spring gardening season and for STEM Friday, we have Dig In! by Cindy Jenson-Elliott and illustrated by ("dirt by") Mary Peterson.

Cindy Jenson-Elliott's new book celebrates the simple pleasures of mucking around in the soil. Each page reveals a new discovery, from earthworms to pill bugs.

With only a few words per page, the text is simple enough to read to toddlers or for beginning readers to tackle on their own.

I dig in the dirt...and find a seed.
Seed waits.
I dig in the dirt...and find a spider.
Spider runs.

The illustrations are linoleum block prints with just the right touch of humor. It might be fun to accompany the book with a quick art lesson using ink stamps or making potato prints to celebrate the illustrations.

It seems that digging in the dirt is a pastime too few young children get to indulge in these days. Dig In! is sure to encourage young readers to get outside and explore the world under their feet.

Related Activity:

Have everyone put on some old clothes and take your children out to a place they can examine some soil. Start by simply sitting on a patch of soil. Ask your children what they think soil is. Is it alive? (Yes, components of soil are alive.) What does it consist of? Are all soils alike? Smell the patch of soil, what do you smell? Touch the soil. What does it feel like? Is it wet or dry? Warm or cool?

Then allow the children to dig into the soil with their hands. Sandbox digging tools can be helpful, but not necessary. If age appropriate, supply a hand lens or magnifying glass. Talk about what they discover.

Some things to look for:

(Links go to related posts with activities)

Sue also has a review and suggestions for related activities at Sally's Bookshelf.


Age Range: 4 - 8 years
Publisher: Beach Lane Books (March 1, 2016)
ISBN-10: 1442412615
ISBN-13: 978-1442412613

Disclosure:  An ARC was provided by the publisher for review purposes. Also, I am an affiliate with Amazon so I can provide you with cover images and links to more information about books and products. As you probably are aware, if you click through the highlighted title link and purchase a product, I will receive a very small commission, at no extra cost to you. Any proceeds help defray the costs of hosting and maintaining this website.

Come visit the STEM Friday blog each week to find more great Science, Technology, Engineering and Math books.


For our regular STEM Friday feature we recommend two books about trees for children, just in time for Arbor Day, next Friday April 24, 2015. (Read the rest of the reviews and see a video book trailer at Wrapped in Foil blog.) Then we'll finish out Butterfly Gardening With Children Week with a discussion of trees for butterfly gardens.

The first book, Branching Out: How Trees Are Part of Our World by Joan Marie Galat and illustrated by Wendy Ding (2014), describes a particular species of tree, how it used by humans, and what animals depend on that kind of tree in a series of four-page spreads. The 11 species of trees highlighted range from red maples and downy birches to pau brasil and cork oaks.

The second book, Celebritrees: Historic and Famous Trees of the World by Margi Preus and illustrated by Rebecca Gibbon (2011), consists of a series of two-page spreads telling the stories of 14 famous, tall and exceptionally-old trees from around the world, the back matter gives more information about the trees and a number of suggestions about what the reader can do to help and encourage trees.

Appropriate for butterfly gardening week:  In the section about oak trees in the back matter of this book, we find out that a single large oak tree can support up to 34 species of butterflies!

That fact reminds us that although growing pretty flowers helps the adult butterflies, to have a truly productive butterfly garden you need to supply food for caterpillars as well.

Many beautiful species of butterflies require trees as larval hosts.


1. Hackberry trees (Celtis species) are larval food for

  • Tawny emperor butterflies
  • Hackberry emperor butterflies
  • Mourning cloak butterflies
  • Question Mark butterflies
  • Snout butterfly

mystery-butterfly-2-identicationThe snout butterfly

Hackberry_Emperor,_Megan_McCarty46Hackberry emperor butterfly (Public domain photograph by Megan McCarty)

(Seed of the Week post about Canyon Hackberry)

2. Live oaks are larval food for California sister butterfly larvae.

California-sister-butterflyCalifornia sister butterfly, Ramsey Canyon, Arizona

Some duskywings and hairstreaks also use oaks for food.

3. Black cherry (Prunus serotina) trees are larval food for:

  • Red-spotted purple
  • Eastern tiger swallowtail
  • Coral hairstreak

4. Citrus trees (orange, lemon grapefruit) attract numerous giant swallowtails. Their larvae are called orange dog caterpillars.

caterpillar-orange-dogAn orange dog caterpillar on a grapefruit leaf

In addition to larval food, trees provide shelter for butterflies (and a multitude of other animals), provide safe places for the caterpillars to pupate, and some flowering trees supply nectar for many more adult butterflies.

In his book, Bringing Nature Home, entomologist  Doug Tallamy gives a list of how many species of butterflies and moths are supported by 21 kinds of trees. The numbers are astonishing! He says oak trees (genus Quercus) provide food for some 534 different species of butterflies and moths. Given that those butterflies are important pollinators and parts of the food web, that is an enormous contribution.


If you are going to plant a tree for Arbor Day or any other event, consider choosing a local species that will host butterflies. You will get yet another benefit from a tree. Please leave a comment if you have any questions about how to choose a suitable butterfly host tree for your area.



 This is the final post for Butterfly Gardening with Children Week. Hope you enjoyed it. If you missed the previous posts from the week, check our links page for topics we covered.


Interested in reading more great books about trees for Arbor Day? Try our giant, redwood-sized list of children's books about trees at Science Books for Kids.



Disclosures: The books above were from my local library. Also, I am an affiliate for Amazon. If you click through the linked titles or ads and make a purchase, I will receive a small commission at no extra charge to you. Proceeds will be used to maintain this self-hosted blog.

Come visit the STEM Friday blog each week to find more great Science, Technology, Engineering and Math books.