How to become a terrarium gardener: build, maintain and look after a mini-indoor garden

If you don’t have a garden, terrariums are a stylish and brilliant way to get hands-on with nature and add some greenery to your home. Here’s an expert guide on how to make and look after the mini-gardens. 

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Nature is a balm in anxious times, so it’s no wonder many of us have turned to the natural world to soothe our souls during the pandemic. The Royal Horticultural Society has reported a huge surge in young people growing their own vegetables for the first time in the last year and waiting lists for allotments have doubled in some areas of the UK.

But for many of us, cultivating our own green space isn’t an option. In fact, one in eight British households has no access to a garden. However, if you’re without a patch of grass and still want to get green-fingered, there’s a very stylish solution.

Terrariums are self-sustaining ecosystems, or mini-gardens, housed in glass jars. Once you’ve built them, the plants inside will happily live in your home with very little attention – you don’t even have to water them.   

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“The idea is that once you’ve watered a terrarium after making it, you never have to do it again,” says Emma Sibley, who owns London Terrariums in New Cross, which sells ready-made terrariums, DIY kits and hosts terrarium workshops.

“When plants photosynthesise in a closed terrarium, the heat and oxygen they produce condensates on the inside of the glass and trickles down the side as water, creating a stable and humid ecosystem. So, they’re perfect for people with busy lives.”

First developed in Victorian times, terrariums hark back to an 18th century trend for collecting ferns and displaying them in bottle gardens or Wardian Cases. The hobby was so popular, the term ‘pteridomania’ was coined to describe the craze.

Use plants that thrive well in humid conditions for your terrarium.

“It’s really come back around,” says Emma. “In smoggy Victorian London, people, especially young women, would escape to the countryside to collect these ferns and bring them home. Now young people today are turning to houseplants to escape from tech and sitting at their desk all day.”

Despite being self-sufficient, terrariums are something you can tend to and nurture for years. “There’s only so much you can do with houseplants,” says Emma. “Once you’ve re-potted it and given it a dust, there isn’t a lot to do. But, putting in the effort to make these mini-gardens is a way to reconnect with nature.”

Here, Emma shares her tips and instructions for making your own terrarium and caring for it, as well as how to create one on a budget using objects you may already have at home.  

What you’ll need to make a terrarium at home      

  • A glass jar or container (preferably with a lid)
  • Peat-free terrarium compost or houseplant compost
  • Activated charcoal
  • Gravel or pebbles
  • Decorative stones or shells
  • Tools, including a patter and long tweezers
  • Carpet moss
  • Humid-friendly plants  

You can build terrariums with a lot of objects that you already have at home. “For the glass jar you could use an old clip-top kilner jar or even an old jam jar,” says Emma.

The tools to care for the plants in your jar can also be ingeniously created from old kitchen utensils. “You can put corks on the end of kebab skewers or gardening canes, which you can use to pat down the soil,” says Emma. “Corn on the cob skewers stuck to the end of sticks are also really good for jabbing out leaves that have fallen in.”

Even the plants you use can be foraged. “You can use moss from your garden wall or garden shed and experiment with plant cuttings,” Emma adds. 

You can create the tools you need to make your terrarium from objects at home.

What kind of plants work best in a terrarium? 

As terrariums are moist, self-contained eco-systems, small plants that thrive in humid conditions grow best in them.

“Most ferns work really well,” says Emma. “A plant called a fittonia is a go-to terrarium plant – they’re sometimes called nerve plants because they have amazing patterns all over their leaves. Mosses and ivy also work really and other plants like ficus camilla that love humidity.”  

How to build a terrarium from scratch  

1. Start by adding a layer of gravel, stones or pebbles to your glass jar

“The gravel is essential for drainage. You need somewhere for the water to go so the compost doesn’t become too sodden,” says Emma. “You can use any garden gravel. Aquarium gravels are also great because you can get them in different colours.

Emma recommends experimenting with different layers of gravel: “Just make sure you don’t go too far up the container because that limits the room you’ve got for everything else.”

2. Sprinkle some activated charcoal over your stones

“Cover the stones in a thin layer of charcoal. A normal kilner jar would usually need a teaspoon, if you’re using something bigger use a tablespoon,” says Emma. “Activated charcoal filters the water as it flows through the closed cycle of the terrarium. But, if you don’t have any to hand, don’t let that stop you.”

3. Add your compost

Next, add your compost to plant your foliage into. “We use a normal peat-free potting compost, but houseplant compost is also fine,” says Emma.

4. Plant your foliage

If you can fit your hand into your jar to do this, the process will be easy. If not, use tools like extra-long tweezers, a cork patter or a terrarium grabber. Make them with things you have at home if you don’t have any professional equipment to hand.

Finish off your miniature garden by covering the soil with moss.

5. Decorate your terrarium

Finish off your miniature garden by covering the soil with some moss or using decorative stones and shells for some flair. “I always think moss really finishes the terrarium off, as do a few decorative stones,” says Emma.

6. Add water

Give your plants a few good sprays of water before closing the lid. This water should be recycled continuously through the garden ecosystem and keep your plants healthy and thriving.  

Emma’s expert tips for making a perfect terrarium  

Don’t overfill your container

Although it’s tempting to pack your container full of beautiful plants, it’s good to leave plenty of space so the foliage has room to grow. “Always pare back,” says Emma. “Take your time over making it. You can also move things around at any point and trim things down.”

Think about gradients

To get your plant presentation perfect, Emma suggests building your compost on a slope: “This will give a prominent front and back to the terrarium. I like to put the taller plants at the back and then smaller plants towards the front. It gives a lovely cascading effect.”

If in doubt, use moss

“We love moss,” says Emma. “Pack lots of it in around your plants and it will always finish off your garden really well.” 

Keep your terrarium somewhere bright to help your plants photosynthesise.

How to care for your terrarium  

Keep an eye on your terrarium in the weeks after making it 

During the fortnight after making your terrarium, Emma recommends taking the lid off for two hours every two or three days. “This allows the plants to settle into the new environment,” says Emma.

Watch for condensation 

Terrariums shouldn’t need too much watering. “As long as you see a light condensation on the inside of the glass you shouldn’t have to water it anymore after giving it a few sprays when making it,” says Emma. If you stop noticing condensation building up on the glass then spray the foliage again.

Avoid direct sunlight 

It’s important to keep your terrarium somewhere bright to help your plants photosynthesise and grow, but do keep your terrarium away from direct sunlight. “It’s good to keep the terrarium away from south-facing windows or take it out of a conservatory, otherwise the plants will quickly melt,” Emma explains.

Trim your plants 

Keep an eye on your plants to make sure they still look healthy. “You can trim your plants down and remove any bad leaves with just a normal pair of scissors,” says Emma. You can also use skewers to remove any fallen leaves making your terrarium look untidy.  

Find out more about how to create and care for terrariums on London Terrariums’ website, or book one of their terrarium-making workshops. For more expert-led guides and tutorials, follow The Curiosity Academy on Instagram (@TheCuriosityAcademy).

  • Emma Sibley, owner and founder of London Terrariums

    Emma Sibley
    Emma Sibley founded London Terrariums in 2014.

    Emma quit her full-time job to found London Terrariums in 2014 out of a passion for gardening but not having a garden in London. Over the past years, the shop has moved from  Bermondsey to New Cross Gate, London. This is their HQ for making terrariums and holding workshops. 

Images: courtesy of Emma Sibley/London Terrariums