As a kid, I loved the tiny worlds of terrariums. I collected colorful moss, interesting pebbles, and all sorts of garden discards to include in my glass jar (usually a giant peanut butter jar with holes punched in the lid.) I often included an interesting beetle, or, in the summer, lightening bugs, to create a miniature habitat to set on my bedside table. In recent years, the popularity of terrariums has surged, and you can now find all sorts of fancy jars filled with exotic, miniature plants to purchase at your local florist. If, like me, a terrarium touches that bit of childhood nostalgia, here are some guidelines for building your own miniature world to enjoy all winter long.
A terrarium can be assembled in any transparent container. I have seen them available in antique glass jars, inverted cloches, mini ornamental green houses, vases and tiny glass bottles (how they get the plants in there is beyond me!) The type of plants you want to include in your terrarium will help determine the type of jar you need. Shade loving mossy habitats require a lidded container. Succulents prefer low walled containers, perhaps a clear pedestaled candy dish. Sun loving plants desire containers with an open top, such as over-sized brandy glasses or pedestaled trifle dishes. Before starting, assemble assorted tools, such as: a spray bottle filled with water, tweezers, pokey sticks, funnels, spoons, scissors, and paper towels.
Begin building your landscape with a layer of rocks suitable to the size of your container. This provides drainage and aeration for the plants you choose. The rock layer is followed by a "filtration" layer which keeps your soil from filtering into the drainage layer. This can be dried moss or activated charcoal. Your soil should be chosen depending on the types of plants you place in your terrarium: peat moss for moss terrariums, sandy, cactus soil for succulent terrariums, or basic potting mix for other mixed plantings.
When choosing terrarium plants, make sure they are small enough to fit into your container. Look for plants that require low-medium light, such as: aluminum plant, polka dot plant (hypoestes), baby tears, small ferns, creeping fig, dracaena or pothos. Place the plant in the soil and tamp down to eliminate air pockets. If your hand doesn't fit into your selected jar, use tongs, tweezers, and chopsticks to aid in planting; place a cork at the end of a chopstick to tamp down the soil around the plants. As a finishing touch, you can add whimsical figures, rocks and sticks to build a scene within your habitat. Use a spray bottle to water your terrarium and to clean the inside of the container.
Caring for your terrarium is easy. Check the soil moisture every week or so. If the soil is dry to the touch, lightly water with your spray bottle. If you have an enclosed terrarium, remove the lid once a month to reduce condensation. Don't fertilize your terrarium; you don't want to encourage vigorous growth in your plants! Pull off any yellowing leaves, and prune back plants as they get too tall for your container.
Robin Trott is a Horticulture Educator with University of Minnesota Extension.