What Is a Terrarium? A Quick Horticultural Handbook

Imagine stepping into a tiny emerald world where lush tropical greenery grows under a closed canopy of glass. Sounds lovely, right?

Well, that’s the essence of terrariums and the topic of our exploration today. 

In this handy guide, we’ll cover exactly what terrariums are, how they work, and what they’re used for. Everything from terrarium plants to ecosystems.

Let’s dive right in at the deep end.

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What is a Terrarium? (Definition and Origins)

Terrariums are miniature gardens housed inside small, sealable glass containers.

As fully functioning plant ecosystems, they’re mostly self-sustaining. The plants water themselves through transpiration and condensation.

The origins of the name come from the Latin terra (“earth”) +‎ arium (a place or receptacle). Like an aquarium, just for plants and earth instead of fish and water.

Makes sense, right?

types of terrarium on table
Terrariums come in many forms these days.

In theory, a perfectly balanced closed terrarium ecosystem can last forever. But it’s challenging to perfectly balance all of the elements of the ecosystem.

To do that, you’ll need to know precisely how a terrarium works.

How Does a Terrarium Ecosystem Work?

Closed terrariums are fully functioning ecosystems – just miniaturized.

Understanding how terrariums work is a basic lesson in the water and carbon cycles.

  • The warmth from the sun causes moisture to evaporate from the plants and soil, which then condenses on the cooler inside surfaces of the glass container. Just like rainfall, the water then drips/falls back down into the soil, and voila! The process starts again.
Seeing fog and condensation on the glass is a good sign of a healthy water cycle.
  • As for nutrients, they’re first added along with the terrarium soil, but – in a fully bioactive terrarium – they are replenished over time as the cleanup crew bugs recycle any waste organic matter.

That said, closed terrarium DIY isn’t an exact science, and it can take a bit of trial and error to get right.

Much like our world’s ecosystems, they can be susceptible to changes in light, temperature, and overzealous species. But with the right design and build, you can build yourself a wonderful little world.

The oldest closed terrarium has lived for decades!

What is a Terrarium Used For?

The concept of the terrarium came about from a botany accident in Victorian London (the history of terrariums is surprisingly exciting).

But in short, they were originally designed to transport live plants across the world.

Naturally, they quickly became a hot new trend as Victorians explored their love for exotic plants and ferns, famously dubbed “Fern Fever.”

I’d say not much has changed, really!

tropical terrarium on windowsill
We like to display our terrariums on the window, just as the Victorians did.

On a practical level, modern terrariums are perfect for people like me who love the natural world but live in a city (with no garden) and have little space for plants. Or for people who’d like a stunning collection of exotic plants that require very little maintenance.

But terrariums have evolved to be so much more than a practical means of growing plants.

Terrarium building is an art form. I like to think of it as the intersection between art and science (and that’s why I love it).

Whether you’re looking for a mossy desktop companion, a contemporary way to liven up your home, or a fun project to do with the kids – terrariums are a fantastic option to explore.

👉 Ready to get started? Check out the terrarium supplies on our online store!

What Makes a Suitable “Terrarium Plant”?

Terrarium plants are as varied as they are beautiful, but they do tend to fit some certain criteria.

Naturally, closed terrarium plants will be tropical species that appreciate the hot and humid conditions of a sealed container. Of course, it tends to help if they’re slow-growing and miniature, too!

Ferns and mosses are your best friends here, but there are all sorts of tiny vines and foliage plants to choose from (the Peperomia genus has both!).

A lot of your typical tropical plants will eventually grow too tall, so opt for dwarf varieties where possible.

Check out my guide, “What is a Terrarium Plant,” for the full breakdown.

tropical closed terrarium
You’ve almost infinite combinations and possibilities!

👉 Alternatively, see our pick of the best terrarium plants for quick, easy-care options.

Over to You

There you have it, an overview of the art and science that is the humble terrarium.

So, what is a terrarium? Awesome, that’s what!

Next up, check out how to make a terrarium (a beginner’s guide), or jump straight in with a DIY terrarium kit.

5 thoughts on “What Is a Terrarium? A Quick Horticultural Handbook”

  1. Thankyou! But can you tell me that,How can plants do photosynthesis in the terrarium if it is closed? Because plants need carbon dioxide to do photosynthesis that is in the atmosphere and if the jar is close so how the plants in the terrarium get Co2 for doing photosynthesis?

    1. That’s a great question! It’s mostly from bacteria in the soil that are breaking down any decaying organic matter and releasing Co2 (also, any breathing bugs if you have them).

  2. Hi! Thanks for the article, it was very informative and helpful for a newbie like me! Quick question, do terratiums still survive in the winter? I live in the UK so during winter it’s mostly freezing cold and hardly any warmth from the sun, so does that mean we will have to water it ourselves?

    1. Hi Brenna, I live in the UK too (the cold North-East) and my terrariums don’t tend to suffer much. Though I do keep quite a warm house. Rather than watering more manually (as it’ll all just pool and build up) it’s better to help the water cycle externally – so I pop my terrarium on a little heating mat to get things moving.

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