When students build and grow their own terrarium, they get hands-on experience of the rainforest habitat--lush plants, high humidity, condensation and drip. A tropical terrarium is probably the easiest living system to create in a classroom.
Materials
clear glass or plastic container, for example an aquarium, large jar, or fish bowl
clear cover for container
aquarium gravel and aquarium charcoal
potting soil (sterile, organically rich soil sold at garden and variety stores)
plants (see our suggestions, below)
spoon for planting
atomizer for watering
optional: small stones or other ornamental objects
How much gravel and soil you'll need depends on the size of your container. Read directions for assembly before you shop.
Wash and then thoroughly rinse your container and cover. Mix gravel and charcoal about 3 parts to one and sprinkle in the bottom of the container to make a one-inch layer. Add two or more inches of soil, depending on how large your container is and how large the root systems of you plants are. Two inches of soil is probably optimal in a closed terrarium. Add your stones or other ornaments (optional).
Spray your soil with water until it is slightly damp. Be careful not to make it too wet.
Dig small holes for your plants and place them, pot and all, in these holes. When plants are arranged, unpot each one and gently put it in place. Fill around roots with more soil.
Cover your terrarium with its own lid or with a sheet of glass (available from hardware stores and window replacement services). If you use sheet glass, bind unfinished edges with electrician's tape.
You may want to seal your aquarium. Make sure that soil is well moistened, and then attach your lid with electrician's tape. Wait a day or two. If walls are completely misted over, you'll need to uncover the terrarium and let it dry out a bit. Experiment until you find a good balance. Walls should be slightly misty at the warmest, sunniest times of day.
Maintenance
If your terrarium is sealed, you probably won't need to water it. Keep it warm (65 to 75 degrees is ideal). Place it within several feet of a sunny window but not in direct sunlight. Most small, tropical plants get twelve hours of indirect sunlight in their natural forests. Eight to ten hours of slightly brighter light will work in your classroom. Supplement natural light with fluorescent if necessary.
If your terrarium is unsealed, watch it carefully and note when soil begins to dry out. Water by misting plants with your atomizer. Most tropical plants tolerate high levels of moisture, but too much watering will cause your soil to mold.
Many tropical plants are hardy and quick growing and will need to be clipped back. Plan to open your terrarium every two to three months to clip back philodendron, impatiens, etc.
Class Activity
After you water, watch the leaves on different kinds of plants. Do they shed water? Why do you think they do this?
Plant Suggestions
The following tropical varieties are easy to grow and available at local nurseries, garden centers, and variety stores. Any of these plants will do well in your terrarium.
Creeping fig
Ficus prumila
Good ground cover that will creep over rocks and other rough surfaces; may grow up your terrarium walls
Croton (over 12 inches)
Codiaeum variegatum
Adds color to your terrarium (pink, scarlet, yellow) but requires more light and can be quite large--good for the sunnier side of a larger container
Earth Stars (1-3 inches)
Cryptanthus spp.
Small and colorful, perfect for all container sizes
Oxalis (3-6 inches)
Oxalis spp.
Clover-like leaves; fire fern (Oxalis hedysaroides 'Rubra' has tiny, brilliant red, fern-like leaves and small yellow flowers.
Philodendrum (vine)
Philodendron spp.
Will fill your terrarium within months; control it by clipping off new growth
Sander's dracaena
Dracaena sanderiana
The corn-like plant with white striped leaves associated with the classic tropical terrarium
Sultana impatiens
Impatiens walleriana
Another hardy grower that can be controlled by clipping back
Sweet flag (6-12 inches)
Acorus gramineus variegatus
Grassy, green and white; likes a little extra light (place on the brighter side of your container)
Table ferns (6-12 inches)
Pteris spp.
Many to choose from
Tropical begonias
Begonia spp.
Many tropical varieties are quite small and will do well in your terrarium with minimum pruning
Wandering Jew (vine)
Zebrina spp.
Adds interesting color; control by clipping back.
Find more plant suggestions at--
University of Missouri Extension
http://muextension.missouri.edu/xplor/agguides/hort/g06520.htm
instructions and a good list of tropical and other plants
Rob's Mini-o-lets
www.robsviolet.com
an African violet nursery that also carries begonias and tropical miniatures
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