Make your own mold terrarium
Build a small mold terrarium using a clear container, soil, bread or fruit scraps, and moisture to observe mold growth with adult supervision.
Step-by-step guide to make your own mold terrarium
Step 1
Gather your materials and bring them to a clean table or counter.
Step 2
With an adult, wash your hands with soap and water before you begin.
Step 3
Use the marker to write your name and today’s date on the lid or side of the jar.
Step 4
Use the spoon to put about a 1 inch layer of potting soil into the bottom of the jar.
Step 5
Press the spoon gently into the soil to make a shallow little pocket in the center.
Step 6
Place the small piece of bread or fruit scrap into the pocket in the soil.
Step 7
Cover the scrap lightly with a thin layer of soil so it is just hidden.
Step 8
Lightly spray or sprinkle water until the soil is damp but not dripping — it should hold together when squeezed.
Step 9
Wipe any water off the jar rim with a paper towel.
Step 10
Put the lid on the jar but leave it slightly loose so air can get in.
Step 11
Put the jar in a warm place out of direct sunlight and out of reach of pets and little hands.
Step 12
Look through the clear jar every day and draw or write what you see with an adult’s help.
Step 13
When you are finished watching the mold grow, have an adult seal the jar tightly.
Step 14
With an adult, put the sealed jar into a trash bag and throw it away safely and then wash your hands.
Step 15
Share a photo and what you observed about your mold terrarium on DIY.org.
Final steps
You're almost there! Complete all the steps, bring your creation to life, post it, and conquer the challenge!
Help!?
What can we use if we don't have a glass jar or potting soil?
Use a clean clear plastic food container with a lid instead of a glass jar and, if you can't find potting soil, use clean soil from a potted houseplant or a store-bought seed-starting mix, then add about a 1-inch layer with the spoon and label the lid with the marker as instructed.
What should we do if the soil gets too wet or the jar fogs up with condensation?
If the soil is dripping or the jar is fogged, open the lid briefly, wipe excess water off the jar rim with a paper towel, let the soil dry until it only holds together when squeezed, then replace the lid slightly loose so air can get in as the steps direct.
How can we adapt the activity for different ages?
For preschoolers, have an adult wash hands, write the name/date, spoon in the 1-inch soil and make the pocket and place the scrap while the child watches and lightly sprinkles water, and for older kids let them do each step independently, record daily drawings or photos, and post observations on DIY.org.
How can we extend or personalize the mold terrarium experiment?
Create two labeled jars using the marker with different scraps (for example bread vs. fruit), place them side-by-side in a warm spot, use a magnifying glass to observe daily changes, and document differences with drawings and photos to share on DIY.org.
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Facts about microbiology and decomposition for kids
⏱️ Some molds can appear on bread or fruit in as little as 24–48 hours when it's warm and damp.
🌈 Mold comes in lots of colors (green, white, black, orange) because different species produce different pigments.
🔬 Mold spores are microscopic and float in the air everywhere — you'll often see growth in a moist terrarium within days.
🌱 Not all fungi are bad — many fungi help break down dead plants and recycle nutrients into soil.
🧪 The first antibiotic, penicillin, was discovered from a mold (Penicillium) in 1928.
How do you build a mold terrarium?
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