Terrariums, glass containers into which you plant a miniature garden, challenge us to find plants appropriate to the small space. Once the plants go in, the terrarium stays undisturbed for months at a time. Ideal plants will grow slowly and at maturity will still fit the container. The terrarium's humidity level also influences proper selection. Open terrariums can support cacti, for example, but a sealed container won't. Lastly, the amount of light the container will receive will also determine what plants are best. When planting a terrarium, try to choose among specimens that have the same environmental needs.
Mosses and Liverwort
Short, spreading plants that reach a maximum size of 3 inches work well in small containers and are perfect for not crowding other plants. Mosses and liverworts are good examples. Besides the benefits of their size, growing moss and liverwort gives a terrarium an old feel, and can increase the sense that a small world exists within the container. They like moisture and low to moderate light. Since the plants will grow beneath other plants, the needed light conditions are not difficult to achieve.
The rosary plant (Ceropegia woodii), which is also called the string-of-hearts plant, is so-named because of its appearance. The leaves are shaped like hearts, while the beads that give the plant its other name of rosary are tubers that grow at the base of stems. The plant likes high light conditions, and also stays at a diminutive height of up to 3 inches. The plant has pink flowers.
Carnivorous plants grow well in terrariums. You will, however, have to actually feed the plants insects. Venus fly trap (Dionaea muscipula) and sundew (Drosera spp.) are good choices for terrariums that will have lots of light and humidity, so a lidded terrarium is the place for the two meat-eating plants. The plants aren't very large, growing less than 6 inches tall.
African violets (Saintpaulia spp.) also grow up to 6 inches and are good for terrariums that will be placed in medium light. There are many varieties available, some with small leaves. These are probably the best choice for your terrarium, unless your container is very large.
Bird’s Nest Sansevieria
Bird’s nest (Sansevieria trifasciata) is a dwarf variety of the snake plant. It grows up to 6 inches tall and wide and tolerates low light. It's a hardy plant with a reputation for surviving the less than tender ministrations of brown thumbs. The plant has a spreading habit.