A terrarium is a miniature garden grown inside a glass container, often shaped like a jar, bowl, or bottle. It matters because it lets students see plant care, design, and environmental science in one small project. A well-built terrarium is not just decoration, since its layers manage drainage, soil health, roots, air, and moisture.
Building one also teaches observation, patience, and how living systems respond to light and water.
Key Facts
- Photosynthesis: 6CO2 + 6H2O + light energy = C6H12O6 + 6O2.
- A closed terrarium recycles water through evaporation, condensation, and dripping back into the soil.
- Layer order usually goes drainage stones, activated charcoal, soil barrier, potting mix, plants, and decorative top layer.
- Closed terrariums usually need indirect light because direct sun can overheat the glass container.
- Drainage layer depth is often about 10% to 20% of the container height.
- Open terrariums are better for succulents and cacti because they allow faster drying and more airflow.
Vocabulary
- Terrarium
- A terrarium is a small garden grown inside a glass or clear container.
- Drainage layer
- The drainage layer is a bottom layer of pebbles or gravel that holds extra water away from plant roots.
- Condensation
- Condensation is the process where water vapor cools and turns into liquid droplets on the glass.
- Activated charcoal
- Activated charcoal is a porous material used in terrariums to help reduce odors and keep water cleaner.
- Microclimate
- A microclimate is the small set of temperature, humidity, and light conditions inside a specific place such as a terrarium.
Common Mistakes to Avoid
- Adding too much water, which is wrong because terrariums have little or no drainage outlet and roots can rot in soggy soil.
- Putting a closed terrarium in direct sunlight, which is wrong because the glass traps heat and can cook the plants.
- Using desert plants in a sealed humid jar, which is wrong because succulents and cacti usually need dry soil and strong airflow.
- Skipping the drainage and charcoal layers, which is wrong because excess water, odors, and poor root conditions become harder to control.
Practice Questions
- 1 A jar is 30 cm tall. If the drainage layer should be 15% of the jar height, how many centimeters tall should the drainage layer be?
- 2 A student adds 120 mL of water to a closed terrarium, but only 40 mL was needed. How many milliliters of extra water were added?
- 3 A closed terrarium has foggy glass all day and the soil looks wet. Explain what this shows about the water cycle inside the jar and name two changes that could help the plants.