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How to Build a Terrarium

Building a terrarium is not a difficult process. But you do need to think about a number of different things to make sure that your terrarium does what you want it to do and looks good over a longer time period.

Building a terrarium

Crafting Your Terrarium: A Step-by-Step Guide

  • Select Terrarium Type
  • Pick Plants
  • Container Choice
  • Prep the Container
  • Create Planting Mix
  • Plant with Care
  • Enhance with Extras
  • Position Thoughtfully

Choose which type of terrarium to build

First things first, to build a terrarium you need to decide which type of terrarium you want or need. There are two main options to choose from and which one you select will largely depend on what you want to grow within the terrarium you build. 

The first option is a closed terrarium, which is a container that will remain sealed for much of the time, allowing for a closed-loop water cycle to occur, and humid conditions to develop. 

The second option is an open terrarium, which is a container with better airflow, that remains more open to the surrounding environment and therefore provides some control over humidity, but broadly speaking a more arid situation. 

You will need to think carefully about which type of terrarium you need, considering this at the same time as the next point on this process – deciding which plants to grow. 

Decide which plants you will grow

The plants that you wish to grow in your terrarium will dictate which type of terrarium you should make. If you are growing tropical rainforest plants, or other plants that like humid conditions, then a closed terrarium will be the right option in most cases. 

If you are growing succulents, cacti or other plants that like less humid and more arid conditions then an open terrarium may be the right choice for you. 

Note though that not all plants will be well-suited to growing in a terrarium of any kind, since they need better airflow than these can provide. So choose plants carefully as well as thinking about the specifics of the terrarium design. 

Choose a terrarium container

Getting a terrarium container sorted can be as simple as just purchasing one that has been specially designed for the purpose. But if you would rather save money and make a more sustainable choice then you can consider a range of DIY options. 

You can upcycle or repurpose a range of items originally intended for other uses to make a terrarium or multiple terraria for your home. 

For example, for a closed terrarium you might use old glass cookie jars with lids, old food preservation jars, glass lidded coffee jars, old apothecary jars, or any other lidded glass container that you may have around your home, or be able to find at low cost from a charity shop, antiques shop, or online. You might also repurpose an old fish bowl or fish tank for the purpose. 

Just remember that a closed terrarium should have a lid of some kind, and should be made from clear glass. Coloured glass will not usually allow enough light to pass through and the plants inside will suffer. 

It will be easier for you to prepare, plant and maintain your closed terrarium if the opening is large enough for you to fit your hand comfortably inside. Though you may be able to purchase or make tools to manage in a container with a smaller opening. 

Open terraria do not need lids, of course and will typically take a more bowl-like form. Any old glass bowls might be used to make one. If you do not have old ones around, you might be able to source one at an antiques shop or thrift store, or online. 

Prepare your container

Especially if you are making a closed terrarium, it is particularly important to make sure that you clean the receptacle that you have chosen very well before use. 

The sealed environment within a closed terrarium can be a breeding ground for micro-organisms, so it is best to create an environment inside which is as sterile as possible to prevent any problems with bacterial growth or fungal disease. 

Wash your container well. It is also best to wear gloves or at least make sure you have very clean hands as you prepare the planting medium and plant up and create your display. 

Prepare a planting medium

The growing medium that you choose will depend on the type of plant that you are growing. Unless you are growing air plants, you will usually put some sterile soilless potting mix in the base of the terrarium. You can purchase a general purpose peat-free potting mix, or make your own and sterilize it in your oven before use to avoid the introduction of pathogens to the closed system.

It is also a good idea to add some charcoal to the medium. This will add organic matter and will also help to absorb any odours. 

To know how much growing medium you will need to add, you will need to have decided which plants you will place in the closed terrarium. The growing medium should be deep enough to just accommodate the roots of the plant with the largest root system that you have chosen. 

Plant up your terrarium 

Once you have decided on your plants, planting it up and creating your display is the most interesting part of the job. Creating a design, you should think about the needs of the specific plants, and group plants with similar requirements. You can also think about the aesthetics, of course. 

It can be interesting to choose, where multiple plants will be placed, specimens with varying heights, and different foliage colour, form and texture. This can add variety. Though take care with a small display not to go overboard, and make things look too busy. 

If the terrarium will be viewed only from one side, taller plants will usually go at the back, with shortest, ground cover plants like moss, for example, to the front. If you will view it all round, taller plants will often go in the middle, with shorter ones around the outside. In certain situations, you may even ‘landscape’ within the terrarium, creating a higher point and lower areas, or sloping the soil up towards one side, for example. 

You can use our imagination and create a display that pleases you.

Decorative features

As well as placing plants in a closed terrarium, you might also add other decorative features, like pebbles or small stones, twigs etc.. Less is often more and too many can make a display look busy and cramped. But you can use your own aesthetic judgement. 

Give your imagination free reign and you can come up with a range of enchanting and attractive displays. Just make sure that you thoroughly clean anything that you place into your terrarium with natural soap and hot water before you place it into the system. 

Position your new terrarium correctly

It is important to think about where you will place a closed terrarium when choosing your plants, since, of course, some plants will require more light than others. A closed terrarium should never be placed in direct sunlight, as this can cook your plants. A good spot will usually be in a bright room, or close to a bright window. But some plants can thrive even in a dimmer spot.