Terrariums can be either sealed with a lid or cork, or open - sealed terrariums for tropical plants that like a warm and humid atmosphere, open ones for temperate plants adapted to dry climates which keep the air in the terrarium free from excess moisture.
I remember as a child in the 1980’s there was a trend for bottle gardens, officially known as ‘Terrariums’ and my mum had a big green one in our living room.
Terrariums are great for people living in small spaces and are really fun projects for kids. I have found them a great way to teach children about the carbon cycle in relation to global warming as the closed system is very well representative of the earth and its atmosphere protected by the ozone layer.
Terrariums are low-maintenance and can be used as a decoration in the house or on a desk in an office and they come in a variety of shapes and sizes.
The first plants never made the long trip back home
Let’s go back in history for a while to the great plant hunting days of the 18C. Ships were being commandeered by botanic gardens, private estate owners and plant nurseries to travel the world in search of new plants.
It was a boom time for horticulture as it meant the arrival of new, non-native and often tropical species arriving into Europe. The only problem was, the first of these plants never made the long trip back home on sea voyages, as many would die from exposure to salt water, lack of light and fresh water.
The plants were packed below deck amongst the other cargo on ships headed back to Europe, untended by crew who resented the space the plants took up.
The Wardian case
This all changed with the creation of the ‘Wardian case’, an accidental discovery by the medical doctor and amateur botanist, Nathanial Bagshaw Ward.
Ward found a fern spore growing in a sealed jar holding a cocoon of moths he was studying in 1829. He realised that these conditions were perfect for the growth and safe transportation of plants - the new glass cases could be kept on deck allowing the plants to receive sunlight.
The specially designed cases also protected plants from salt water, but allowed condensed moisture to reach the plants. With time and testing these cases were further developed to better protect the plants.
The invention of this safe way to transport plants was vital for the development of international trade, making it possible to transplant commercially significant plants from their native habitats and introduce them to cultivation for new countries and new markets.
They transported the first tea plants from China to India, and rubber and cinchona (the plant from which quinine is derived, used in the treatment of malaria) from South America to British colonies in Asia. Not to mention the thousands of newly discovered plant species that grace our gardens and homes still to this day.
Ferns and mosses are ideal plants to grow in a closed terrarium
Closed terraria create a unique environment for plant growth, as the transparent walls allow for both heat and light to enter the terrarium. It creates a small scale water cycle as moisture from the respiring plants and soil condense on the inside wall of the terrarium which drips back down into the soil for use by the plants.
The light that enters through the glass allows the plants to photosynthesise, converting light energy into chemical energy in the form of sugars and carbohydrates to be used for growth.
Ferns, mosses, air plants, carnivorous plants and dwarf palms are ideal plants to grow in a closed terrarium as they are slow growing and love the sealed humid environment.
A little air and a little water
It’s good to open the terrarium once a week to allow excess moisture out of the container as it prevents mould and algal growth which can damage the plants and grow on the inside of the glass which reduces the amount of light getting into the system.
They should be watered too as and when required, and a good indicator of this is the absence of condensation on the inside of the glass, and plants that look like they are wilting.
A quick guide for making a terrarium
You will need:
- small stones or pebbles, for the base layer to help drainage
- soil, potting soil where most soils will work fine for this
- activated charcoal, if you can get some as this will keep the terrarium water fresh and avoids bacteria growing
- a selection of small tools, pencil/chopstick, little trowels, long spoons
- decoration, stones, moss makes a colourful base, or little objects
- plants, of course
- In a clean and dry container, layer up some pebbles to about 2-3cm,
- Top tip: vary your design by turning the container on its side instead, so the lid is pointing to the side rather than upwards.
- Next add the charcoal. You only need to scatter it across. (If you have some sphagnum moss, you can add it after this).
- Add the potting soil. Ensure there is enough, so the plant roots sit comfortably deep inside it.
- Your biggest plant goes in first.
- Using your small trowel, or long-handled spoon, make a hole for the plant.
- Gently place the plant into the soil. You can use a pencil-like tool to fill in and flatten the soil around it.
- Make sure your plant has enough room to grow a little; don’t cramp them against the glass.
- If you have more, keep adding the rest of your plants.
- Place in other stones, or maybe some moss or sand to cover up the soil if you want to.
- Put in any finishing touches.
- Close the lid.
A fun project when your fingers are itching
That’s all there is to it really and you can be as inventive as you like. There are so many types of glass containers - some which are sold specifically as terrariums, but old glass jars or larger pasta jars serve the purpose just as well.
Many types of decorative stones are found in stores and garden centres and of course those from the garden or whilst out on a walk. There are even long handled planting tools that can be fitted through the small neck of one of those big bottle garden jars to help in planting the plants.
The little terrarium found in my house serves as a lovely reminder of those epic plant hunting days of the 18th C and I often put it on my desk and stare at it whilst writing articles just as this one.
It´s a also a fun little project to do over winter when fingers are just itching to get in the soil and they make great gifts for friends and family, especially to those who you scratch your head when thinking what they might like for Christmas.
So what are you waiting for? Go find a glass container, some pebbles, stones, a handful of soil and don’t forget the plants!
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