What you'll need:
- Glass container
- Sheet Moss (optional)
- Potting Soil
To create your own terrarium, try fish bowls or tanks, flea market glass jars, or a container designed to be a terrarium. The container should be at least 6-8” deep. Whatever size you use, it helps if your hand can fit through the opening!
Place a piece of sheet moss in the bottom of the container to absorb excess water (optional). Next, spread gravel, preferably a natural kind like pea gravel, an inch or two thick (this keeps the soil from absorbing excess water and staying too soggy, it's also optional). Putting a layer of sheet moss or burlap over the gravel will keep the dirt that goes on top from seeping into the gravel. Next, spread about a quarter-inch layer of charcoal over the gravel to absorb odors. Then add at least two inches of potting soil, or more depending on the types and sizes of your plants.
Finally, place your plants in the soil. Smaller containers will hold two or three, and some might hold only one. Use very small, relatively hardy plants that do well in medium moisture environments and low to moderate light, like pothos, ferns, moss, ivy and bromeliads. (If you want to use cactus in your terrarium, make sure the lid is removable.)
You can add gravel, sand, pebbles or moss to complete your terrarium "landscape".
Place your terrarium in bright indirect light—direct sun on a terrarium may cook your plants. Water or mist the terrarium sparingly, but keep it barely moist (unless it’s a cactus terrarium). If you're using a container with a cover, monitor the terrarium for a month or two to make sure it does not get too moist (condensation will form on the glass, and mold and fungus might appear on the plants and in the soil). Adjust the lid opening, or remove it, to temper the amount of moisture; eventually it should stabilize, and the terrarium won’t need as much care. Terrariums without lids require more water and care, as moisture is lost to evaporation.
Terrariums need maintenance to keep the plants balanced in size. Most plants sold as "terrarium plants" are simply young plants that will eventually grow to their full size. You can replace these with new young plants, and repot the growing plants to use as houseplants. For some slower growing plants occasional trimming will work for a while, but keep in mind you will need to replace plants eventually as they grow.