Terrariums are miniature ecosystems that add life to any room in your home or office. Closed terrariums are especially easy to care for after they've been planted, because they retain much of their own moisture. The keys to choosing the right plants for a closed terrarium are to pick ones that tolerate high moisture, low light, remain small enough to suit your chosen container and are beautiful to look at.
Closed terrariums are humid environments and the plants used in them should be suited to these conditions. Mosses are commonly used in terrariums as ground cover because they love moisture, don't need much light and don't have roots that take up space in the soil. Most ferns will also do well with high humidity. The variegated spider fern (Arachnoides simplicior Variegata) makes a good terrarium plant. It can grow up to 16 inches tall and wide, so if it proves too large for your container, it will have to be moved to a larger one or planted outside.
Low Light Options
Because the plants in closed terrariums are covered, they often receive less light than other houseplants. You can place your terrarium under a light to nurture plants that require a bit more brightness. The starfish plant (Cryptanthus bivittatus) can thrive with little light. Variations in light levels produce different colors in its leaves, which may be green, red or white. Because this plant grows to a maximum size of 6 inches tall, it's ideal for a closed terrarium. Golden club moss (Selaginella kraussiana Aurea) isn't a true moss, but it is a brightly-colored ground cover for closed containers. It only grows to about 2 inches tall, but it can spread rather wide, so should be trimmed to prevent it from overtaking your terrarium.
Terrarium plants need to have a small maximum size and must be considerate of their cohabitants' space. Moon Valley friendship plant (Pilea involucrata) grows to a maximum height of 12 inches. It is also a decorative plant, with serrated-edged leaves that have a crinkled texture and a distinctive red vein on the leaves' undersides. It may even produce small pink flowers, if conditions are favorable. Begonias (genus Begonia) are a common choice for terrariums, often growing only 6 to 10 inches tall. Dwarf rex begonias (Begonia rex-cultorum) are popular in containers because of their small size, year-round blooms, and multicolored leaves.
Plants in a variety of textures, heights, colors and shapes add visual interest to your terrarium. Joseph's coat (Codiaeum variegatum) is a vertical plant that grows long, pointed, multicolored leaves in dark green, pink, orange and yellow. This is a larger plant, so Joseph's coat is best for bigger terrariums. Prayer plants (Maranta leucoreura) also have decorative leaves, with stripes of light and dark green and pink veins. African violets can be a colorful addition to a closed terrarium. With endless varieties in size, leaf shape, flower color and pattern, African violets (genus Saintpaulia) provide a multitude of options when designing your container. All they need is a bit more light than most terrarium dwellers.
Plants to Avoid
Succulents and semi-succulents will eventually rot in closed terrariums, because they require so little moisture and a closed terrarium remains humid. Succulents grow better in open terrariums or dish gardens. Climbing plants can push the lid off the glass enclosure, disrupting the ecosystem for the other plants and possibly even breaking the lid. Plants with large roots or roots that send up shoots can quickly take over the limited soil available to your other plantings.
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