Types of terrariums:
Other – be creative! Fish bowls, light bulbs, vases, mason jars, etc.
Permanent or temporary? Design your garden accordingly
Permanent – tropical plants, orchids, ferns, mosses.
Temporary – forced bulbs, veggies, annual plants. Make it easy to pull apart and replant when the display is done.
Use fresh, sterile potting media
Don’t use the stuff from your garden. It will come full of bugs you don’t want inside, and probably won’t drain well enough or hold enough moisture.
Adding sheet moss to the sides, top, or bottom of your terrarium can help regulate moisture by wicking up any excess, although it is not necessary.
Add some horticultural charcoal to the soil. This will help prevent stagnant soil and mineral build up.
Choose your plants wisely.
Look for dwarf or slow-growing varieties, or things that can be easily pruned.
Consider light and water requirements and choose plants accordingly.
Plants that do well in terrariums:
Many tropical plants
Anything that likes high humidity
Some plants that don’t do well in enclosed terrariums:
Anything that needs good air circulation
Choose plants of varying color, leaf size, and texture for visual interest. Don’t choose too many differing elements, however, or the design will look too busy.
Consider getting some tiny tools, especially if your container is very small. Plastic spoons and forks are helpful, as is a cork on a thin stick for tamping down soil.
Adding props such as fairy garden items, shells, dinosaurs, or interesting rocks can make your design more fun.
Give your design a finished look by mulching with moss, gravel, bark, sea glass, or whatever else strikes your fancy.
Water very carefully! Because most terrariums are enclosed they keep moisture for a very long time. When moisture is needed only add a tablespoon or two at a time. They are very easy to water log.
If you are getting too much condensation leave the opening ajar to ventilate as needed.
Be careful if your terrarium gets direct sun. They can easily overheat and cook the plants inside.