Building a terrarium is a rewarding way to bring a miniature, self-contained ecosystem into your home. The first and most critical step in this process is selecting the right plants, as not all greenery thrives in the humid, low-airflow environment of a enclosed glass container. The success of your design hinges on choosing species with similar care requirements, specifically their need for high humidity and low direct light.
Understanding Closed vs. Open Terrariums
The fundamental question guiding your plant selection is whether you are creating a closed or open terrarium. This distinction dictates the entire ecosystem your plants will live in. A closed terrarium features a lid or is left completely enclosed, creating a humid environment reminiscent of a tropical rainforest. Conversely, an open terrarium lacks moisture, favoring plants that prefer arid conditions and excellent airflow.
Plants for Closed Terrariums
Closed terrariums are ideal for tropical plants that enjoy consistent moisture and high humidity. These plants typically feature lush, verdant foliage rather than large flowers, as the goal is to create a sustainable, low-maintenance landscape. The sealed environment reduces the need for frequent watering, making these specific varieties particularly resilient indoors.
When selecting greenery for a sealed glass container, look for species that naturally grow in shaded forest understories. These plants are adapted to low light levels and thrive in the damp conditions that would cause other houseplants to rot. Ferns, mosses, and small-leaved tropicals are the gold standard for this application.
- Fittonia (Nerve Plant): Prized for its striking veined leaves in shades of red, pink, and white, Fittonia is a perfect choice for adding color to a green landscape.
- Peperomia: These compact plants come in a variety of textures, from fleshy leaves to trailing varieties, and they adapt well to the terrarium environment.
- Selaginella (Spike Moss): Despite the name, this is not a moss but a vascular plant that thrives in humidity and can recover from drying out better than most true mosses.
- Baby’s Tears (Soleirolia): An excellent ground cover with tiny round leaves that form a dense mat, perfect for covering the soil and creating a lush appearance.
Plants for Open Terrariums
If you prefer an open vessel or a dish garden, you must select plants that crave dry air and infrequent watering. Standard houseplants that require high humidity will quickly develop root rot or fungal issues in an open, humid-free container. The best candidates for these setups are succulents and cacti, which store water in their tissues and are drought-tolerant.
- Haworthia: These small, architectural succulents feature translucent leaves that allow light to reach deeper tissues, making them visually interesting without requiring much space.
- Echeveria: With their stunning rosette shapes and variety of colors, Echeverias add a dramatic focal point to any dry terrarium.
- Sedum: Hardy and easy to care for, Sedum varieties offer a range of textures and colors, from deep purple to light green.
- Christmas Cactus: While slightly more demanding than true cacti, this Schlumbergera appreciates the well-draining soil of a terrarium and produces beautiful flowers.
Mosses and Lichens
No matter the terrarium type, mosses and lichens are invaluable components of the design. They act as natural mulch, helping to retain moisture in the soil while preventing erosion. Additionally, their neutral color palette provides a beautiful contrast to the vibrant greens and textures of flowering or variegated plants.
Sheet moss and cushion moss are popular for covering soil in humid environments, while reindeer moss is actually a lichen that maintains a sponge-like texture. These elements are crucial for creating a natural, forest-floor aesthetic that enhances the visual depth of the miniature landscape.
Essential Companion Elements
Plants cannot survive in a terrarium without a proper foundation. The choice of substrate is just as important as the selection of the foliage above it. A standard terrarium requires a drainage layer—typically composed of pebbles or activated charcoal—situated above the potting soil. This layer prevents the roots from sitting in water, which is the primary cause of decay in enclosed environments.
When arranging your plants, consider their mature size and growth rate. Place taller specimens toward the back or center of the container, and allow trailing plants to cascade over the edges. Grouping plants with similar water and light needs ensures that no single element in the ecosystem is stressed, leading to a harmonious and long-lasting display.
