How to make a terrarium that won’t die in 6 weeks

September 24th, 2017
Posted In: Container gardening

The terrarium is back in fashion. You probably last saw one in the 1970s, gathering dust in Great-aunt Agatha’s musty Victorian interior.

Now you might expect to find them in hipster home stores, or on Pinterest and Instagram.

Terrariums are back

Terrariums are back in fashion. This one was created by lifestyle blogger, Jeska, of the Lobster And Swan blog in our blogger workshop with James Wong and Fiskars.

But, according to TV botanist James Wong, most of today’s terrariums are doomed to die in six weeks. ‘I found more than 100 images of terrariums on Pinterest,’ he said. ‘And I didn’t think any of them were planted well enough to survive more than 6 weeks.’

The Sky Garden at London's Walkie Talkie building

We met James in the Sky Garden in London’s ‘Walkie Talkie’ building. It’s free to visit, but you have to get timed tickets.

So Fiskars Garden Tools sponsored a small group of lifestyle/garden bloggers – including me – to meet James at the Sky Garden in London and write a post on his tips for a successful terrarium.

Note: there are some affiliate links in this post, which means you can click through to buy. If you do, I may receive a small fee. I only link to products I’ve tried myself or which are highly rated.

How long should a terrarium last?

The longest lasting terrarium - 1963-2014

James Wong showed a sealed terrarium, which grew happily from 1963-2014 without ever being opened, watered or fed.

And terrariums changed the world we live in today

May I briefly digress into history before giving you James’ tips for making a fab terrarium?

Before Dr Nathaniel Bagshaw Ward invented the terrarium in 1833, it was difficult to ship plants around the world. On deck they were blasted by salt air and wind. Below deck, plants died without light.

Then Nathaniel Ward observed a fern and some moss growing in a sealed jar. He designed and built a ‘Wardian Case’, which was like a greenhouse in a box. It was completely sealed and created its own environment. It was effectively the first terrarium.

The Wardian Case was used to transport plants all over the world. Without it, we wouldn’t have the rubber plantations of Malaysia, the tea industry in India and more (and without the rubber industry, we wouldn’t have the motor car!)

So the terrarium is more than just something which goes in and out of fashion.

How to make a terrarium

First, you need the right container. It needs to be big enough, said James – a minimum of 30cm squared. And it can be square, round or bottle-shaped, but not pyramidal. They don’t need to be sealed, but if they’re not, you do need to water them (not too much!).

The wrong shape for a terrarium.

James Wong illustrating the ‘wrong shape’ for a terrarium. When I googled ‘terrariums’ there did seem to be alot of pyramidal ones out there.

We were given a choice of square and round terrariums to plant. They measured around 25cm high/diameter.

Choose a large enough terrarium

My empty terrarium. It’s around 23 cm high with a diameter of 26cm at its widest. To the right are a lightweight plastic fork and trowel (seen here: Fiskars Grow Urban Planters set), plus super-long tweezers. Top left you can see snippers for delicate work – use deadheading or flower-arranging snippers.

House plant or terrarium garden tools

House plant garden tools for making your terrarium

I had trouble finding slightly larger terrariums online, but this pentagon terrarium is about the same size.

Quite a challenge to take home on the train – but much more likely to survive longer than 6 weeks.


A small plastic (or other non-sharp edged) lightweight spade, plus snippers or small scissors for trimming plants in a confined space. (We used Fiskars Herb & Flower Snips). Add long pair of tweezers and a small container or funnel for adding the soil to the terrarium.

Adding grit for drainage

Lori from parenting/lifestyle blog Wild and Grizzly and  Hannah from the Seeds and Stitches blog get started- adding grit and soil to their terrariums…Instagramming the process….and two James Wongs apparently look on.

Drainage and soil…

You need a base layer for drainage in your terrarium. James chose some lightweight clay pebbles, called hydroleca.

First, add a drainage layer of grit to your terrarium

This is the right amount of hydroleca to provide drainage for your terrarium.

And being mean with the soil is another common terrarium mistake, according to James. You need a good 30mm of potting soil. Use an ordinary multi-purpose house plant compost – there are several brands available, such as Westland or Levington.

Add enough soil to your terrarium

Add sufficient soil to your terrarium.

Choose your plants carefully

Glass filters UV light, says James. Which means that a terrarium is suited to shade-loving plants, not sun-loving ones like cacti. You can’t get round it by putting the terrarium in direct sunlight either, as it will heat up too much.

Secondly, you need small plants. Not young ones. There is a difference.

Plant at an angle for realism

To make your terrarium look natural, James advises that plants grow naturally at an angle. Don’t plant everything growing straight upwards.

When I googled ‘best plants for a terrarium’, I discovered recommendations for plants like Areca palms, which may start off small, but which grow up to 3ft-6ft high.

James bought a selection of plants for us to choose from. They included Mini ferns, peperomia, helxine (known as Mind Your Own Business) plus moss and airplants.

Terrarium design tips

James said that we needed to start with a theme, and that he would judge our terrariums ‘along RHS Chelsea rules.’

That means that you aren’t judged according to whether the judge likes your garden, but on whether you fulfilled the brief.

I decided to choose ‘Australia’ as my theme.

And the other thing to remember, says James, is that human beings were originally ‘forest edge dwellers.’ Our early ancestors probably lived at the edge of the forest, using the trees for shelter and to hide from predators. But we needed open spaces in order to forage for greenery and hunt for game.

Balance greenery and 'open space'

Lifestyle blogger, Melanie, of the ‘slow living’ ‘Geoffrey and Grace’ blog working out the ideal balance between greenery and open space.

The ideal human landscape, he says, is at least one-third open. Don’t stuff your terrarium with wall-to-wall plants.

Different heights

Few landscapes are completely flat. So add different heights to your terrarium.

So James produced lightweight tufa rocks and miniature spiderwood branches to help us make our terrariums three dimensional.

Create different heights in your terrarium

Bloggers adding twigs and tufa to create different heights.

Cover all the earth

Bare earth doesn’t exist in nature, according to James. He gave us a choice of adding moss or gravel – or both, so that we didn’t leave any bare earth.

Gravel for terrariums

A good tip from James: in nature gravel comes in lots of different sizes. In shops, gravel is sold in packets of a similar size. Buy two different sizes of gravel to look realistic.

An hour later…

We finished, and James came round to judge us.

Me and my terrarium.

Me and my terrarium. This theme business isn’t as easy as it sounds. I’d originally planned to create something like my brother-and-sister-in-law’s hillside garden in Australia, which is green with tree ferns and conifers. I ended up thousands of miles out, creating a desert. Respect to Chelsea garden designers for sticking to a brief.

James was encouraging about all the terrariums, but awarded the well deserved first prize to Stephanie Donaldson of The Enduring Gardener blog for her ‘Borrower’s Jungle’ (based on The Borrowers, the novel about miniature people).

Prize-winning terrarium

Stephanie Donaldson and The Borrowers’ Jungle.

Terrarium on Instagram

And here’s my terrarium, all Instagrammed (I gave it a retro filter – Nashville – in hommage to the terrariums of my university days…) If you fancy connecting on Instagram, join me here.

And afterwards…

Then James advised us to soak the compost thoroughly, using a small watering can, but not to water more often than once a fortnight after that. ‘You can see if the compost looks dry,’ he added. ‘That’s the time to water.’ However, it’s a good idea to spritz the leaves with water every few days, too.

Place the terrarium somewhere reasonably light, but not in strong direct sunlight.

But if your terrarium doesn’t last fifty years, that doesn’t mean you’re a terrible gardener. ‘Plants die,’ says James cheerily. ‘I’ve killed thousands.’

How to create an indoor jungle…

The biggest trend of the last few years is that after about a decade of the ‘garden as an outside room’, we are now entering the era of the home as an ‘inside garden.’

This means pot plants, terrariums, air plants, grow kits and more. It’s fuelled by the fastest-growing group of new plant buyers today – the ‘Millennials’ (those who became young adults in the early 21st century). For some inspiring ways of displaying indoor plants, see How to Decorate With Indoor Plants. 

Those of us who are not Millenials find house plants nostalgic. It’s like taking a trip back to the interiors of the 1970s...

And here are some tips on finding the pots and planters to go with your indoor plants.

Pin to remember how to make a terrarium

And do join us. See here for a free weekly email with tips, ideas and inspiration for your garden.

How to make a terrarium that won't die in six weeks

3 comments on "How to make a terrarium that won’t die in 6 weeks"

  1. Karen Milne says:


Leave a Reply

Your email address will not be published. Required fields are marked *

− 4 = 5