Succulents are popular in indoor gardening, prized for their diverse textures and minimal water needs. These drought-tolerant plants store water in specialized tissues, allowing them to survive in arid environments. A terrarium is a collection of plants housed within a clear glass container, designed to create a self-contained, often humid, microclimate. Combining the desert-adapted succulent with the moisture-retaining environment of a terrarium is fundamentally mismatched.
Why Terrariums Are Not Suitable
The primary reason succulents fail in a terrarium is the lack of proper airflow, which creates a humid and stagnant atmosphere. Terrariums, especially closed designs, trap moisture released through transpiration and evaporation, leading to high ambient humidity. Succulents evolved for dry conditions and cannot tolerate persistent moisture surrounding their leaves and stems.
Continuous dampness invites destructive pathogens, making the plants susceptible to fungal diseases and bacterial rot. The stored water inside the plant, combined with the humid exterior, causes the plant to decompose, often starting at the root level. Even open terrarium designs restrict air movement significantly compared to an open pot. This reduced air circulation means the potting medium remains wet for too long, leading directly to the decline and death of the succulent.
Understanding Succulent Environmental Requirements
Succulents require an environment that allows for rapid drying, which terrariums actively prevent. The most important feature for a healthy succulent container is a drainage hole, which is absent in traditional glass terrariums. Without this exit point, excess water collects at the bottom of the container, saturating the roots.
Attempting to compensate by adding a layer of pebbles or charcoal at the base is ineffective and detrimental. This practice creates a “perched water table,” where water is held within the soil layer just above the gravel, remaining saturated. The water does not pass through until the entire soil column is saturated, leaving the roots in a perpetually waterlogged zone.
Beyond drainage, succulents demand low ambient humidity to prevent fungal growth and require a dry period between waterings. They also need intense light. Placing them in a low-light terrarium causes etiolation, where the plant stretches unnaturally toward the light source. The resulting growth is pale, weak, and elongated, permanently compromising the plant’s compact structure.
Successful Open Container Gardening Alternatives
To successfully cultivate a decorative garden of succulents, gardeners should use a shallow, open planter instead of a terrarium. The container must have at least one functional drainage hole to allow excess water to exit immediately after watering. Porous materials like unglazed terracotta or concrete are recommended because they allow moisture to evaporate through the container walls, helping the soil dry faster.
The correct soil mixture is equally important; standard potting soil retains too much moisture and is too dense. Instead, use a specialized cactus and succulent mix formulated to be fast-draining. This commercial mix should be amended further by cutting it with non-organic materials in a 50/50 ratio.
Amending the Soil Mix
Non-organic materials include perlite, pumice, or coarse sand. Adding these significantly increases porosity and air content. These “dish gardens” or shallow bowls mimic the arid conditions succulents thrive in, providing quick-drying soil, ample air circulation, and space for intense light exposure.