How to make a terrarium that won’t die in 6 weeks
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.
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.’
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?
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.
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!).
We were given a choice of square and round terrariums to plant. They measured around 25cm high/diameter.
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.
Drainage and soil…
You need a base layer for drainage in your terrarium. James chose some lightweight clay pebbles, called hydroleca.
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.
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.
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.
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.
The ideal human landscape, he says, is at least one-third open. Don’t stuff your terrarium with wall-to-wall plants.
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.
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.
An hour later…
We finished, and James came round to judge us.
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).
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.
Last week I looked at the 2018 garden trends. The biggest one 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).
While I’m definitely no Millennial, I’m excited about this new direction for plants. I really enjoyed learning about terrariums from James (thank you, Fiskars!).
And if your terrarium doesn’t last fifty years, that doesn’t mean you’re a terrible gardener. ‘Plants die,’ says James cheerily. ‘And I’ve killed thousands.’ After all, gardening is a learning process….