Succulent Terrarium — Open vs Closed and Why It Matters

Succulents in closed terrariums die from excess humidity while open terrariums can thrive beautifully. Learn the right way to create a succulent terrarium that actually survives. This guide covers everything you need to know about this topic, including common causes, step-by-step solutions, and answers to frequently asked questions.

Here are the key things to understand: Closed terrariums trap humidity at 80-100% which rots succulents within weeks — never use a sealed container. Open terrariums with wide mouths allow airflow and evaporation making them safe for succulents. The most popular succulent terrarium container is a geometric glass terrarium with open panels. Drainage is critical since most terrarium vessels lack drainage holes — use a thick charcoal and pebble false bottom. Succulents in terrariums need less water than potted ones because the glass walls reduce evaporation. Understanding these fundamentals will help you diagnose and resolve this issue more effectively.

The most common reasons this occurs include: Closed or narrow-mouth terrariums trap moisture creating a humid microclimate that rots succulent roots and stems. No drainage layer causes water to pool at the bottom creating a swamp condition hidden below the soil line. Using regular potting soil instead of gritty succulent mix retains too much moisture in the enclosed space. Overwatering is amplified in terrariums because excess water has nowhere to drain or evaporate. Identifying the root cause is the first step toward finding the right solution.

To resolve this, follow these recommended steps: Choose an open container with a wide mouth — the wider the opening, the better the airflow for succulents. Layer the bottom with 1 inch of pebbles, then a thin layer of activated charcoal to filter water and prevent odor. Add 2-3 inches of fast-draining succulent or cactus mix on top of the drainage layers. Plant small slow-growing succulents like echeveria, haworthia, and small sedums with space between each. Water extremely sparingly — use a syringe or squeeze bottle to target the soil around each plant, never on leaves. If these steps do not resolve the issue, consider consulting additional resources or a qualified professional.

This article is part of our Succulents & Cacti collection on Houseplants Wiki. We provide comprehensive, up-to-date information to help you find solutions quickly.