A completely enclosed terrarium requires little or no watering, but if in doubt always water less. If the soil is completely dry and the leaves are wilting this is a sign that the terrarium is too dry and needs watering. NEVER pour water into your terrarium. Water should be added a little at a time using a misting bottle to avoid overwatering as there is nowhere for excess water to go.
If your terrarium has large droplets of condensation on the glass then it has plenty of moisture and shouldn’t be watered. If this happens, remove the lid and make sure that it receives adequate light and airflow across the opening to aid drying. However, keep in mind that a balanced terrarium will have some moisture on the glass. If the terrarium glass is clear, check if your terrarium needs watering by placing your finger in the top moss layer as well as into the moss to the soil underneath. If the moss and/or soil is beginning to dry out, mist the terrarium in small doses. Larger terrarium plants can receive extra water with a spray bottle at the base of the stem to ensure water gets into the soil underneath the moss layer. N.B. you can always add more water but can’t remove it so easily!
What we do:
We check moisture levels in our closed terrariums every 4 weeks during winter months, and check them every 2 weeks during the summer months. If there is still moisture in the system and nothing is wilting or drying out, then we hold off watering. Excess moisture is the enemy of enclosed terrariums!
As the system is enclosed, we only add a few squirts from a spray bottle at a time. We replace the lid after watering and allow the moisture to spread through the terrarium for approx 48 hours before checking it again to see whether its had enough water or needs A little more (if so repeat this process). By watering in this way, you reduce the risk of overwatering which is the main killer of enclosed systems.