Things You'll Need
Long stick or knitting needle
If you plan to make a closed terrarium, be careful not to add too much moisture when assembling the project. While a closed terrarium creates its own self-watering ecosystem, if there is too much moisture plants can begin to rot and mold form. You can use a bottle to create a closed terrarium, because the opening is typically very small. It's a bit tricky adding the necessary materials, due to the limited space of a bottle and its opening. Use a funnel with a long stem spout, to help you position your plant material.
Wash the bottle with soap and hot water and rinse thoroughly. Starting with a clean bottle helps prevent introducing harmful bacteria to the terrarium's environment.
Fit a funnel into the bottle's opening and pour gravel into the bottle. Add enough gravel to make a 1- to 2-inch layer. Jiggle your bottle to settle the gravel into an even layer.
Add a 1/4-inch layer of activated charcoal over the gravel. Pour it through the funnel, and move the funnel in a circular motion inside the bottle, aiming the stem spout to position the gravel.
Insert a long narrow stick into the top of the bottle and use it to move the charcoal around, if necessary, to make an even layer.
Pour potting soil into the bottle, using the funnel. Add a 2- to 3-inch layer of soil. Use the long stick to position the soil evenly over the charcoal.
Poke the long stick into the center of the soil to make an indentation for the plant.
Insert a small houseplant, suitable type and size for a terrarium, through the top of the bottle, and drop it root-first into the indentation.
Move the soil with the long stick, to cover the roots and position the plants.
Insert a spray bottle nozzle into the bottle's opening and spray the inside walls as well as the plant with water to remove any dirt debris and add moisture to the terrarium. Moisten the soil without making it wet or soggy.
If you don’t have a funnel, make one by rolling a piece of stiff paper into a funnel shape.