Guide
Closed vs open terrarium
By Paul Reaney · Updated 7 July 2026
It is the first decision you make and it changes everything else — the plants, the watering, the light, the upkeep. Here is the short version: a closed terrarium is a sealed, humid jar for tropical plants that waters itself; an open terrarium is an airy, dry bowl for succulents that you water yourself. The rest of this page is the detail.
| Closed terrarium | Open terrarium | |
|---|---|---|
| How it works | Sealed jar or bottle. Recycles its own water in a closed cycle. | Unsealed bowl or dish. Moisture escapes; air moves freely. |
| Watering | Almost never — a correctly sealed build can go months. Add a splash only if it looks dry. | Regularly. It has no water cycle, so you top it up like a potted plant. |
| Humidity | High and constant — a warm mini-rainforest. | Low, matching normal room air. |
| Best plants | Humidity-lovers: ferns, moss, fittonia, baby’s tears, selaginella. | Dry-air plants: succulents, cacti, haworthia, air plants. |
| Light | Bright but indirect only — direct sun cooks a sealed jar. | Tolerates brighter light and some direct sun (great for succulents). |
| Mould risk | Higher — trapped moisture. A springtail clean-up crew keeps it in check. | Lower — airflow keeps things dry, but pests find it more easily. |
| Upkeep | Very low once balanced — mostly hands-off. | Low, but hands-on: watering and the occasional trim. |
| Best for | A self-sustaining tropical scene you rarely touch. | Succulents, a sunny spot, and quick easy builds. |
What is a closed terrarium?
A closed terrarium is a sealed glass container — a jar, bottle or lidded vessel — that traps moisture inside. Water evaporates, condenses on the glass and drips back down, creating a self-sustaining cycle that recreates a warm, humid rainforest floor. Set up correctly, it needs almost no watering and can look after itself for months. The trade-off is that trapped humidity invites mould, so a clean-up crew of springtails and good indirect light matter.
What is an open terrarium?
An open terrarium is an unsealed bowl, dish or wide-mouthed vessel where air moves freely and moisture escapes. Because there is no water cycle, you water it yourself — but the airflow keeps humidity low and mould rare, which is exactly what succulents, cacti and air plants want. It is the easier build and the one to choose if you love a bright, sunny, desert look.
The one rule that decides it
Pick the terrarium type to match the plants you love — never the other way round, and never mix the two climates in one vessel. Humidity-lovers (ferns, moss, fittonia) will slowly crisp in an open bowl; succulents and cacti will rot in a sealed jar. If you cannot decide, decide on the plant first: succulents → open; tropical foliage and moss → closed.
Which should you choose?
Choose closed if you want a lush, tropical, low-effort scene that mostly runs itself and you are happy to keep it out of direct sun. Choose open if you love succulents and cacti, have a bright or sunny spot, or want the simplest possible first build. Both are great for beginners — it comes down to the plants and the light you can offer.
Know which one you want? Browse plants filtered to exactly that setup — with photos and care notes for each.
New to this? Start with the best terrarium plants for beginners.
FAQ
Is a closed or open terrarium better for beginners?+
Both are beginner-friendly, but they suit different people. A closed terrarium is more forgiving day to day because it waters itself — set it up right and it is nearly hands-off. An open terrarium is simpler to build and harder to over-humidify, but you have to remember to water it. If you want low maintenance, go closed with tropical plants; if you love succulents, go open.
Do closed terrariums need watering?+
Barely. A properly sealed closed terrarium recycles its own moisture and can go weeks or months without water. You only add a little if the glass stops fogging and the substrate looks dry. Open terrariums, by contrast, need regular watering because moisture escapes.
Can you put succulents in a closed terrarium?+
No. Succulents and cacti need dry air and airflow; the trapped humidity of a closed terrarium will rot them. Succulents belong in an open terrarium. Put ferns, moss and fittonia in a closed one instead.
Which lasts longer, an open or closed terrarium?+
A well-balanced closed terrarium can be self-sustaining for years with almost no input, which is its main appeal. An open terrarium can last just as long but depends on you watering and tending it consistently.
Can I convert an open terrarium to a closed one?+
Only if the plants suit it. Adding a lid traps humidity, which suits ferns and moss but will kill succulents and cacti. Change the lid and the plants together, not just the lid.