A terrarium jar is a miniature landscape. The plants inside are chosen not just for their appearance but for the fact they share the same climate needs. Terrariums come in two varieties---the closed terrarium and the open terrarium. Plant humidity and warmth loving plants in a closed terrarium and everything else in an open version. A benefit of terrariums is that that pets and children can't get to the plants inside. Most terrariums require little care beyond occasional watering.
Choose a clear glass container for your terrarium. Use a 1-quart or 1-gallon canning jar, an empty fish bowl, or any other glass container that is large enough for your desired plants.
Wash the container in hot water with dish soap added. Rinse in a solution of 1 part bleach to 15 parts water and then rinse well.
Place a 1- to 2-inch layer of pea gravel in the bottom of the container. Place a one-half-inch layer of horticultural charcoal, available at garden stores, on top the gravel to keep the soil fresh smelling. Cover this with a thin layer of sphagnum moss so the soil doesn't slip in between the gravel and charcoal.
Fill the container with soil until it is one-quarter full or has at least 1.5 inches of soil. Use a sterilized potting soil or combine 1 part peat moss with 1 part sterilized compost.
Remove all damaged leaves and stems from the plants before placing in the terrarium. Inspect them to ensure there are no visible insects, eggs or diseased areas.
Plant each plant in the soil so the top of the roots are level with the top of the soil. Gently firm the soil around each plant. Place moss and other ground covers around the plants after they are all planted.
Water the terrarium by misting lightly with a spray bottle. Mist again the next day until there is a quarter of an inch of water in the bottom of the container. Cover the container after the second watering if applicable.
Keep the terrarium in indirect sunlight. Remove the lid if the inside becomes too moist or if rot occurs so the soil can dry out slightly. Water closed terrariums every four to six months and open terrariums every two to four weeks.