Being a gardener of a certain age, I have seen garden trends come and go. Terrariums were all the rage in the 70’s but fell out of favor through the 80’s. Now, they are making a resurgence and are more beautiful than ever due to an ever-widening availability of spectacular plants. Assembling a terrarium is a great multi-generational afternoon activity and a wonderful way to introduce children to gardening.
In simplest terms, a terrarium is a transparent glass or plastic container planted as a garden. Growing plants in glass containers date back 2,500 years to the Greeks. However, scholars credit the modern versions to a 19th century physician, N.B. Ward. He was interested in growing different types of ferns and found the greatest success when he inadvertently planted some in a glass jar. “Wardian cases,” as they came to be called, were the means of transporting plant specimens back and forth from Europe and the New World.
Fish bowls, brandy snifters, bottles, or any clear glass container make great terrariums. You can purchase special terrarium containers, but most thrift stores offer a wide variety of substitutes at a greatly reduced price. Frosted or colored glass is not suitable since it filters light and is unsuitable for plant growth. The opening should be large enough to enable you to manipulate the material during planting. A traditional terrarium will have a cover; clear plastic wrap will work if glass is not available. Open containers with a large opening will work, but will require more watering. Open terrariums do tend to have less problems with disease.
Begin by sterilizing your container. Wash it in hot soapy water, run it through a dishwasher cycle, or wash with a 1:15 bleach/water solution. In all cases, rinse thoroughly.
Assemble your materials. Commercial potting soil or African violet potting soil are both good choices. In addition, you will need some small gravel (pea gravel), horticultural charcoal, and sheet or sphagnum moss. Since you are working in a small space use of a kitchen spoon, dowel, tongs, or a rod with a wire loop on the bottom will help you place plants.
When choosing plants, make sure they are disease and insect free. Some plants suited for terrariums are: creeping fig (Ficus pumila), ivy, (Hedera helix), ribbon plant (Dracaena sanderiana), bromeliads, (Cryptanthus, Billbergia, Aechmea species), prayer plants (Maranta species), miniature peperomia, (Peperomia specie), and African violet, (Saintpaulia ionantha). Unless you are planting an open container, avoid succulents and cacti because of the high humidity.
Begin your terrarium with a 1–3 inch layer of gravel at the bottom. Sprinkle about one-half inch of charcoal on top of the gravel and cover with moss. Now, add the soil until approximately one-fourth to one-third of the container is filled with drainage material/soil. Make sure there is a minimum of 1 ½ inches of soil.
Using your tools, make small holes in the soil and insert the plants. Pat the soil around the roots. Add rocks, pieces of wood, and other small accessories to enhance your terrarium.
After planting, mist the garden to clean off the plants and settle the soil. Leave the cover off until the leaves are dry, then replace it. A closed container will only need water a few times per year. Check periodically for rot, disease, or overgrown plants. Remove or trim any troublesome plants.
Terrariums usually last about a year. At that point, they need to be refreshed, rebuilt, and possibly completely redesigned.
Certified Master Gardener