Experiments & Fun Activities

Planting a Terrarium

A terrarium is a miniature landscape in a covered, transparent container. A dish garden is similar, but a dish garden is planted in a shallow, open container. The terrarium is a modern version of the Wardian case, developed by Nathaniel Ward in London in the 1800’s. His curiosity for getting ferns to survive in sheltered environments inspired him to get a carpenter to build him glass cases in which the plants could be grown. Soon all of England adopted these cases, or terrariums to grow ferns and exotic plants from around the world.

You need

  • Container – Any transparent container with a wide opening, such as a wide mouth jar, commercial/ industrial food jars or an old aquarium.
  • Soil - Use a mixture of one part coarse builders sand, one part peat moss, and one part potting soil; garden soil is too heavy for plants to grow well.
  • Plants – There are lots of choices. Garden centers sell dwarf forms of many tropical houseplants. Some possibilities include
    • English ivy
    • Swedish ivy
    • ferns
    • peperomia
    • coleus
    • baby’s tears
    • African violet
    • prayer plant
    • asparagus fern
    • Chinese evergreen
    • nerve plant
    • prayer plant
    • strawberry
    • begonia
    • oxalis
    • bloodleaf
    • Succulents are generally not used in a terrarium, because of their need for dry conditions. But with careful attention to watering, it can be done.
  • Washed, fine gravel, pebbles, or coarse sand
  • Activated charcoal
  • Sphagnum moss
  • Glass cover

What to do

  • Prepare the container by washing with hot, soapy water and rinsing it well.
  • Planting consists of four layers. The bottom layer is for drainage. Place one inch of the gravel on the bottom of the container. For deeper containers, use three inches. On top of drainage layer, spread a thin layer of activated charcoal. Place a thin cover of sphagnum moss on top of the charcoal to prevent the soil from shifting down into the drainage layer. The final layer is the soil – place several inches on top of the moss. The bottom three layers should be laid out evenly. The soil can be contoured for a more realistic look.
  • Your terrarium will be more interesting if you design it to follow some type of theme such as woodland, tropical, bog, etc. Place the plants in natural groupings. Start with the largest plants to anchor the scene. Fill in with the rest of the plants. Try various arrangements before you firm the soil around the roots. If the terrarium will be viewed from one side, build up the moss and soil toward the back of the container. Place larger plants toward the back and cluster smaller ones toward the front. If viewed from all sides, the taller material should be in the center. Use natural groupings – regular spacing looks unnatural. Because the environment within the terrarium is moist, ‘slips’ or cuttings of plants can be inserted and they will root easily. Once the plants are in place, cover the surface of the soil with more sheet moss.
  • When you are ready to plant, remove plants from containers; trim off dead leaves and remove excess soil to expose roots. Trim off roots if plant was rootbound. Set plants, fan the roots out over the potting mix, and firm roots around soil. A cork fixed to the end of a stake provides a suitable tamper.
  • Accessorize your terrarium with pebbles, small pieces of wood, or figurines if appropriate. The accessories should be in scale with the plants.
  • Carefully moisten the soil and mist the plants to wash off any soil that sticks to the leaves or sides of the container. Repeat misting next day, then cover the terrarium to prevent moisture from escaping.

Caring for your terrarium

  • The terrarium should not need water for 4 to 6 months. Water only when the fogging stops or the plants become wilted; then only add small amounts every 2 or 3 hours until wilting stops. If a large amount is added all at once, there is greater danger of over-watering. If there is water in the bottom, leave the top off for several hours per day. Don’t replace the cover until the wet foliage has dried.
  • Place the terrarium where it receives bright but never direct sunlight. Direct sunlight on a closed container will cause heat buildup that will injure most plants. You also can keep the terrarium under artificial plant lights for 12 hours per day.
  • Rotate the terrarium to keep plants growing straight.
  • Trim plants that get too large to maintain shape and condition; remove crowded plants.
  • Fertilizer is not needed for at least a year. Use fertilizer in very small amounts since the plants grow slowly and you don’t want them to outgrow the container. Use a water-soluble type at 1/4-rate.

<< Return to Experiment/Activity Index