What Is a Terrarium? The Complete Horticultural Guide

Terrariums are miniature gardens housed inside small – and usually sealable – glass containers.

As fully functioning (albeit tiny) plant ecosystems, they’re mostly self-sustaining with the plants watering themselves through transpiration and condensation.

Science!

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

So, what is a terrarium? Well, they are a beautiful, engaging, and creative way to keep plants in the home.

Whether you’re looking for a 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.

Let’s dig in.

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Terrariums originally came about from a botany accident in Victorian London (in fact, the history of terrariums is surprisingly exciting).

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

Not much has changed, really!

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). Seriously, the number of potential terrarium ideas and types of terrariums to explore is endless.

How long do terrariums last? Well, a perfectly balanced closed terrarium ecosystem can (in theory) last forever. To do that, you’ll need to know precisely how a terrarium works.

Closed terrariums are fully functioning ecosystems – just miniaturized.

Understanding how terrariums work is a 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.

• As for nutrients, they’re first added along with the 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!

These days, terrariums come in all shapes and sizes.

Jars, bottles, fish tanks; pretty much anything clear can be used as a terrarium container.

Generally, types of terrarium are dictated by what plants you try to grow in them. Tropical terrariums, succulent terrariums, orchid terrariums – you get the idea.

You could also argue that “open” and “closed” are types of terrarium.

• Closed terrariums are the classic type. Sealing off the terrarium and creating a closed system is what perpetuates the ecosystem (and lets us do all the fun things). After all, trapping humidity in terrariums first allowed the Victorians to grow their interesting tropical plants.

• Open terrariums are a modern take on the model. Typically an open dish or bowl, these are great for growing arid plants like succulents and cacti. Though not a terrarium in the functional sense, they still have their place as horticultural art.

The sky is the limit when it comes to generating homemade terrarium ideas.

Previously driven by Pinterest (and most likely now by TikTok), there are some super creative people out there making terrariums out of everything from old Tic Tac boxes to snow globes.

In the case of DIY closed terrarium ideas, there opens up a range of bioactive options too.

Fancy adding some vibrant-colored isopods to the mix? They’ll help keep the terrarium clean, and they’ll look good doing it!

Then, if you’re going large, there’s a different world of opportunity.

From sculpted backgrounds to waterfall features, the size and space really help in creating naturalistic landscapes. You can even consider adding animals (e.g., reptiles) if you want to take it to the next level.

Terrarium plants are as varied as they are beautiful.

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 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 our Best Terrarium Plants for Beginners article if you need some quick picks that have easy care requirements.

Thanks to the booming hobby, it’s never been easier to find terrarium plants for sale online.

I tend to do most of my plant shopping on Etsy. There’s a vast range, and it’s great for getting terrarium plant ideas and inspiration too.

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 Terrarium Kit.