Let’s make a mini greenhouse! This self-sustaining little ecosystem will look fantastic on your desk or in your bookshelf.

Glass jar with lid containing a plant in soil and a toy dinosaur.

You will need

  • Newspaper or paper towel
  • Large glass container and lid. It needs to be at least 20 centmetres high, and wide enough that you can easily fit your hands in
  • Small, slow-growing plant. We used a dwarf peace lily, but you can ask at your local plant store for recommendations
  • Small stones
  • Sphagnum moss (available from plant stores)
  • Potting soil
  • Activated charcoal (available from plant stores)
  • Pencil/chopsticks
  • Long spoon
  • Decorations, like cool rocks or small plastic animals (optional)


Be careful with your glass container and wear closed-toe shoes. If your glass container breaks, ask an adult to help you clean up the pieces. Wash your hands after this activity.

outdoor hazard icon

What to do

  1. Clean and dry your container.

    Glass jar and lid drying on the sink.
  2. Lay down some newspaper or paper towel to protect your space from mess.

    All the items prepared for the activity on a bench.
  3. Put rocks and pebbles into the container, making a layer 2 centimetres high.

    Jar with small layer of pebbles in the bottom.
  4. Sprinkle the activated charcoal over the rocks, making a layer that’s about ½ a centimetre high.

    Jar with layer of pebbles and layer of soil in the bottom.
  5. Soak a handful of sphagnum moss in fresh tap water for about 5 minutes. Squeeze out the excess water and add the moss on top of your charcoal layer. You should get a layer about 1 centimetre high.

    Sphagnum moss soaking in a bowl.
  6. Next, add about 3 centimetres of potting soil. Make sure you use fresh potting soil, like what you can find at gardening stores. If the potting soil is dusty and dry, make it a bit damp so you don’t breathe it in!

    Layers of pebbles, soil and sphagnum moss in a jar.
  7. Use your spoon to make a hole for your plant near the centre so it has room to grow. The hole should be deep enough for the roots to extend downwards.

    Spoon in jar with layers of soil.
  8. Remove your plant from the plastic pot it comes in. Carefully tease the roots apart and remove some of the old soil. Place the plant in the hole you made.

    Small plant with roots exposed.
  9. Use your pencil or chopstick to move soil around your plant so that it is filled in and the surrounding soil is flat.

    Poking plant and soil in jar with a chopstick.
  10. Add decorations! These could be nice stones, small plastic animals, moss, or anything you can think of that fits nicely inside your container.

    Glass jar with lid on containing a plant in layers of soil with a toy dinosaur.
  11. Close the lid.

  12. Wash your hands carefully with soap.

  13. Place your terrarium in a bright spot, but not directly in the sunlight.

    Glass jar with lid on containing a plant in layers of soil with a toy dinosaur.
  14. Tend to your terrarium by spraying it with a little water every fortnight or so.

  15. Keep an eye on it. It’s okay if water sometimes drips down the inside of the glass, but if you can see water pooling down in the pebbles, it’s a bit too damp and you should leave the lid off for a day or so.

What’s happening:

Your terrarium is like a mini ecosystem! Each of the layers you created has a role to play in sustaining the micro-environment for your plant.

First, the rocks jumble together in a way that leaves gaps between the individual stones. This creates space for extra water. Without the rocks, there’d be a risk of your plant’s roots getting waterlogged.

Second, there is some evidence that activated charcoal fights harmful bacteria, but scientists are not sure if this works in terrariums. At the very least, the charcoal looks nice as a layer.

Third, the sphagnum moss absorbs water from the terrarium’s micro-environment and transports it into the soil above. This makes water readily available to your plant.

Fourth, the potting soil anchors your plant while also feeding water and nutrients to your plant’s roots.

Finally, sunlight powers photosynthesis, which is how your plant makes food. During photosynthesis, your plant releases oxygen. Surprisingly, your plant needs that oxygen again when it turns that food back into energy!

Thanks to all these layers, your terrarium can keep going for years with very little work.

The first terrarium:

Did you know that the first terrarium was created by accident? The first one was built to house a moth cocoon and just happened to have a fern inside, too. The fern survived without any added water for 3 years! This discovery in 1833 allowed scientists to make large glass terrariums that could transport live plants across great distances for scientific study.

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