Open vs Closed Terrarium: Which Should You Make?
Open or closed terrarium? Choose a closed terrarium for small, slow-growing tropical plants that enjoy high humidity. Choose an open container when you want more ventilation or plan to grow plants that prefer drier conditions. The lid changes the entire care routine, so decide on the plants before buying the container.
What is the difference between an open and a closed terrarium?
A closed terrarium has a lid that retains humidity and lets moisture recirculate. An open terrarium exchanges air with the room, so its substrate normally loses moisture more quickly. Neither is universally better: the right choice depends on the plant species, available light, size of the vessel and how much maintenance you want to do.
| Feature | Closed terrarium | Open terrarium |
|---|---|---|
| Best suited to | Humidity-loving tropical plants | Plants needing more ventilation |
| Watering | Infrequent once balanced | Usually more frequent; check actual substrate |
| Container | Clear vessel with a suitable lid | Open-top glass vessel |
| Common mistake | Overwatering or overheating | Assuming every open bowl suits succulents |
| Best beginner advantage | Visible moisture cycle | Easy access for adjustments |
Which plants work in a closed terrarium?
Small fittonias, some peperomias, compact ferns and suitable mosses can be effective choices. Prioritise plants with similar moisture and light requirements and check their mature dimensions. The Royal Horticultural Society recommends small, slow-growing tropical foliage plants for sealed containers. Its terrarium growing guide explains the reasoning.
Can you put succulents in a closed terrarium?
Generally no. Many cacti and succulents favour drier substrates and stronger airflow; high humidity in sealed jars makes maintenance difficult. An open display may be more appropriate, but remember that a glass bowl without drainage holes can still retain excess water. Choose substrate, watering and light for the actual plant species.
How often do you water each type?
There is no safe universal interval. According to the RHS, a well-balanced closed terrarium may need only small amounts of water a few times per year. Observe condensation, plant condition and substrate moisture instead of following a weekly calendar. Open containers lose moisture more quickly but also vary widely with species and location.
What size container should you choose?
A wider opening makes it easier to plant, prune and remove debris. A larger closed vessel can also make moisture conditions easier to balance than a tiny jar. Before buying, check the height of the mature plants, the depth needed by their roots and whether you can reach the plants for maintenance.
Where should the terrarium be placed?
For many tropical terrarium plants, bright indirect light is a sensible starting point. Direct sunshine can heat glass rapidly and scorch foliage, especially in a sealed vessel. Never assume a closed jar belongs on the sunniest windowsill.
Five beginner mistakes to avoid
- Choosing the glass first. Match the vessel to the plants instead.
- Mixing incompatible plants. Desert species and moisture-loving ferns do not share the same ideal conditions.
- Overwatering. A gravel layer cannot empty water from a container without a drainage hole.
- Using direct sunlight. Glass can trap heat and damage plants.
- Ignoring mature growth. A plant that fits on day one may quickly outgrow a miniature display.
Which should a complete beginner start with?
If you like tropical foliage, begin with a generously sized closed glass jar, one or two small compatible plants and a modest amount of moisture. If you want to grow drier-environment plants, begin by understanding their drainage needs rather than treating an open decorative bowl like an ordinary plant pot.
Frequently asked questions
Is a closed terrarium completely self-sustaining?
No guarantee. While moisture can recycle for long periods, light, temperature, growth and decay still matter. Observe plants and intervene when needed.
Does an open terrarium need a lid?
No. The lack of a seal is what allows more air exchange.
Should I use activated charcoal?
It is optional, not a substitute for suitable plants and measured watering. Learn more in our soil-layer guide.
Start your own project
Ready to try the humid version? Follow our step-by-step guide to making a closed terrarium, compare beginner-friendly plant options and keep our troubleshooting checklist handy.
How this article was prepared
This is a research-based comparison. It draws on the RHS terrariums and bottle gardens reference and the RHS practical terrarium project. We have not performed a controlled side-by-side growing experiment, and we do not present illustrations as evidence of a firsthand test.