Not every plant survives a closed terrarium. Find out which species to avoid and which ones actually thrive in a humid, self-sustaining ecosystem.
Not every plant thrives in a closed terrarium: succulents, cacti and most Mediterranean herbs will rot within a few weeks in this warm, humid mini-ecosystem, because they actually need dry air and dry roots. Plants that love high humidity and filtered light - such as ferns, fittonias and calatheas - do the opposite: they flourish behind glass. In this article we explain which plants you're better off skipping, why that is, and which species genuinely suit a closed terrarium.
A closed terrarium is essentially a mini-ecosystem in glass: water evaporates from the soil and leaves during the day, condenses against the glass, and then 'rains' back down onto the soil. That creates constant, high humidity and keeps the soil moist without frequent watering. For plants that naturally grow in humid, sheltered conditions - think forest-floor species from tropical regions - that's an ideal climate. For plants that need dry, well-ventilated conditions instead, the same environment becomes a problem: the roots stay wet for too long, there's too little air circulation, and the light is often more indirect than these plants are used to. The result is root rot, mould, and eventually a dead plant.
Succulents and cacti are adapted to drought: their roots and stems store water and rot quickly once they sit in damp soil for a long time. In a closed terrarium, where the soil almost never fully dries out, that often shows up within a few weeks as soft, translucent stems.
Rosemary, lavender and thyme naturally grow on dry, sunny, windy slopes. They need plenty of air circulation and dry air to stay healthy. The high humidity in a closed terrarium quickly leads to mould on the leaves of these herbs.
Plants like a monstera or a mature ficus lyrata grow too fast and too big for a closed glass environment. Within a few months they're already pressing against the glass, which stunts growth and causes damp patches on the leaves with no airflow to dry them out.
Flowering plants generally need more air circulation than a closed terrarium provides. Without enough airflow around the blooms, mould quickly forms on the petals, so the flowers rot prematurely instead of fading gracefully.
The plants that thrive best in a closed terrarium actually love the conditions described above: high humidity, filtered or indirect light, and compact, slow growth. Think ferns, fittonias and the ficus ginseng bonsai. Our Teddy terrarium, for example, deliberately combines a Calathea Lancifolia with a Fittonia White Tiger: both species are used to a humid, shaded forest floor and actually grow better inside a closed glass environment than in an ordinary room.
Prefer to put together your own selection instead of a ready-made kit? Take a look at our terrarium plants collection: it only lists species specifically suited to a closed, humid environment.
Already have a plant at home and wondering whether it belongs in a closed terrarium? Start by looking at where it originally comes from. If it grows in the wild in a dry, sunny, windy spot, chances are it will rot in a closed glass environment. If it comes from a humid, shaded forest floor instead, it's far more likely to do just as well - or even better - in a terrarium than in an ordinary pot on the windowsill.
There are a few clear signs that a plant doesn't belong in your closed terrarium: a stem that turns soft and translucent near the base, leaves with a grey or white fuzz of mould, or a plant that's already pressing against the glass within a few months. If you notice this, it's better to swap out that specific plant for a species that does suit a closed ecosystem, rather than leaving the whole setup permanently open - doing so loses the terrarium's self-sustaining effect.
Want to know more about which species do work well, and why? Our article on which plants you can use in a closed terrarium goes deeper into the best choices per light level and jar size.
It's not recommended. Cacti and succulents need dry air and dry roots to stay healthy. The constant humidity in a closed terrarium leads to root rot in these plants.
The plant usually develops a soft, rotting stem or mould on its leaves within weeks to months. This can spread to the other plants in the terrarium, so it's wise to replace a poorly chosen plant in good time.
Ferns, fittonias, calatheas and the ficus ginseng bonsai thrive beautifully in a closed, humid environment, as shown by the Calathea Lancifolia and Fittonia White Tiger combination in the Teddy terrarium.
Yes - even with well-matched plants, it's common practice to open the terrarium for a few hours about once a month for fresh air, so the moisture balance stays in check.
Still not sure which plants suit your closed terrarium? The Teddy terrarium kit mentioned above already comes with a plant combination chosen for you, ready to go straight away.
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