Succulent terrariums are a popular way to display these drought-tolerant plants, but the enclosed glass environment presents a significant challenge to their care. Succulents naturally thrive in arid conditions, yet a terrarium inherently creates a humid, non-draining microclimate. This conflict means that watering is the most important, and often the most difficult, aspect of maintaining a healthy succulent terrarium.
The Unique Environment of Terrarium Succulents
Caring for succulents in a terrarium is fundamentally different from standard potted plant care because the glass container imposes physical constraints. The most significant issue is the absence of drainage holes, meaning excess water collects at the bottom. This trapped moisture drastically increases the risk of root rot, the leading cause of death for succulents.
Limited airflow within the glass vessel further complicates the situation by slowing the natural rate of evaporation. This lack of air movement causes humidity to build up, maintaining a moist environment that succulents cannot tolerate. Terrariums are typically constructed with a base layer of pebbles or gravel, followed by activated charcoal and a gritty soil mix. These layers are intended to keep the roots separated from standing water and help filter the environment, but they do not eliminate the need for cautious watering practices.
Determining When to Water
The secret to proper watering lies in waiting for the correct moment, which is much less frequent than with other houseplants. Succulents store water in their leaves, allowing them to endure periods of dryness. Wait until the soil is completely dry, and then wait an additional few days to ensure the plant has used up its reserves.
Since a finger test for soil moisture can be difficult in a deep or narrow vessel, rely on other indicators. A practical method is to monitor the overall weight of the terrarium; a dry container will feel noticeably lighter than one with saturated soil. The plants themselves offer the most reliable visual cues: healthy leaves appear full and firm, while thirsty succulents will deplete their internal water stores, causing the leaves to look wrinkled, puckered, or deflated. Also check for condensation; if moisture clings to the glass walls, the environment is too humid and watering should be postponed until the glass is clear.
Precision Watering Techniques
Because of the lack of drainage, the goal of watering a terrarium is not to fully soak the soil, but to provide a small, measured amount of water directly to the plant’s root zone. This is best achieved using specialized tools that allow for precise application. A long-spouted squeeze bottle, a pipette, or a syringe is ideal for delivering water exactly where it is needed without splashing the leaves or the container sides.
This method is known as “micro-dosing,” involving applying only a few milliliters of water per plant. Direct the water to the base of the plant, soaking the soil around the roots while keeping the foliage and crown dry to prevent stem rot. If your terrarium is large, rotate the vessel slowly as you water to ensure even distribution of moisture to all plants. A common mistake is using a spray bottle, but misting the surface only encourages shallow root growth and does not properly hydrate the root system.
Recognizing and Remedying Watering Mistakes
Since the margin for error is small, it is important to quickly distinguish between the two main watering mistakes. Signs of overwatering include leaves that become translucent, yellow, or mushy, feeling soft and squishy. In severe cases, the stem or roots may turn black, indicating that lethal rot has begun.
Conversely, an underwatered succulent will exhibit shriveled, wrinkled, or crispy lower leaves, as the plant consumes its own stored water. If you notice signs of underwatering, apply a small amount of water using the precision techniques described. If the plant shows symptoms of overwatering, stop watering immediately and take corrective action. This includes increasing airflow by removing the lid or opening the container for several days to allow moisture to evaporate. If a plant is visibly rotting, carefully remove the affected plant and replace the saturated soil to prevent the rot from spreading.