A terrarium is a self-contained, miniature garden environment encased in glass, offering a unique way to cultivate plants indoors. These small ecosystems create distinct conditions for plant life, ranging from high humidity rainforests to dry, arid deserts. Selecting the correct plant species is paramount for the long-term success and health of the miniature world. This guide provides an overview of the plant choices best suited for the two primary types of terrariums.
Understanding Terrarium Environments
The confined nature of a terrarium imposes specific environmental constraints that dictate which plants will thrive. All terrariums, whether open or closed, must be placed in a location receiving bright, indirect light. Direct sunlight can quickly overheat the glass enclosure and scorch the foliage. Plants chosen must also be naturally slow-growing or dwarf varieties to prevent them from rapidly outgrowing the limited space and requiring constant pruning.
The primary difference between terrarium types is the level of atmospheric moisture and airflow. Closed systems create a high-humidity microclimate with limited ventilation, which is ideal for tropical species that thrive in consistently moist conditions. Open systems, which lack a lid, promote air circulation and allow excess moisture to escape, favoring plants that prefer drier soil and lower humidity. Understanding these differences is the basis for successful plant selection.
Ideal Plants for Closed Terrariums
Closed terrariums mimic the conditions of a tropical rainforest floor, making them ideal for moisture-loving plants that thrive in high humidity and low light. These systems create a continuous water cycle where moisture evaporates, condenses on the glass, and “rains” back down, recycling water efficiently. Plants chosen for this environment must tolerate consistently moist soil and air saturation.
Ferns are a classic choice for closed terrariums because they naturally inhabit humid, shaded areas. Varieties like the Maidenhair Fern (Adiantum raddianum) and the Rabbit’s Foot Fern (Davallia fejeensis) are excellent options. The delicate foliage of ferns thrives in the stable, moist air provided by a sealed container. Mosses, such as Carpet Moss (Hypnum) and Cushion Moss (Leucobryum glaucum), act as a lush groundcover that contributes to the high humidity.
Small, colorful tropical plants known as “jewel box” species also flourish under these conditions. The Nerve Plant (Fittonia albivenis), with its striking vein patterns, is particularly suited due to its preference for high humidity and consistent soil moisture. Miniature varieties of the Arrowhead Plant (Syngonium) and the Creeping Fig (Ficus pumila) provide trailing or climbing texture. Their high moisture tolerance makes them unlikely to suffer from root rot in this perpetually damp setting.
Suitable Plants for Open Terrariums
Open terrariums, which feature a large opening or no lid, are suited for plants that require drier conditions and greater air exchange. The lack of a seal prevents the buildup of excessive moisture, making this type unsuitable for tropical plants. Plants that prefer arid or semi-arid environments are the most appropriate choice, as they are adapted to dry soil and low atmospheric humidity.
Succulents are the most popular group for open terrariums. Species like Echeveria, Haworthia, and the Jade Plant (Crassula ovata) are excellent selections. These plants store water in their fleshy leaves, allowing them to tolerate the drier soil conditions of an open container. Cacti are also viable, provided the container allows ample airflow, as they are prone to rot in humid or waterlogged conditions.
Air Plants (Tillandsia) are unique additions to open terrariums because they are epiphytes that do not require soil. They absorb moisture and nutrients through specialized leaf structures. While placed inside the container for display, they must be removed periodically for watering (typically by misting or briefly soaking), and then allowed to dry fully before being returned.
Maintaining Terrarium Plant Health
Long-term success in a terrarium depends on diligent monitoring of moisture and growth. Overwatering is the most frequent cause of failure, especially in closed systems, leading to root rot and fungal growth. For closed terrariums, condensation should be visible but not so heavy that water is constantly dripping down the sides. If the glass is consistently fogged, the lid should be slightly opened for a few hours to allow excess humidity to escape.
Pruning is a regular necessity to manage the limited space within the glass container and prevent plants from touching the walls or crowding each other. Overgrown foliage should be clipped back to maintain the intended scale and promote better air circulation. Prompt removal of any dead or yellowing leaves is important, as decaying organic matter can harbor mold and attract pests.
Pest infestations, though less common in sealed environments, may still occur. Fungus gnats are a primary concern, particularly in open terrariums with moist soil. These pests thrive in damp conditions, so allowing the top layer of soil to dry out slightly can help control their population. For any infestation, physical removal of the pest or the affected plant is the preferred method, as chemical sprays can be harmful to the contained ecosystem.