What is a Terrarium?
Terrariums are miniature indoor gardens, usually housed inside glass containers, which create a tiny, thriving ecosystem for the plants within them. Terrariums are low-maintenance, long-lasting, high-impact, living, breathing displays that are scientifically proven to improve mental health, soothe anxiety, purify the air, and they look stunning too!
They make excellent gifts, and look beautiful on coffee tables, bookshelves, or even mounted on walls. They are also great if you’re limited on space as they can be however large or small you like, from a tiny single plant setup to a show-stopping six-foot display!
Here’s our ultimate guide to creating your terrarium, and 21 incredible plants to grow inside.
The History of Terrariums
The word ‘terrarium’ comes from the Latin words terra, meaning ‘earth’, and arium, meaning ‘place’ or ‘receptacle’. They have been a beloved pursuit of botanists and horticulturalists for over 150 years. The first-ever terrarium was invented by accident in 1842 when English botanist Dr. Nathaniel Bagshaw Ward was keeping a moth pupa in a sealed jar. He noticed that the moss and ferns he had placed inside were flourishing in the enclosed conditions. After some experimentation and observation, he published a book on terrarium care, then known as ‘Wardian Cases’. Victorian Britons were rather enamoured with these miniature gardens, and they became very popular. 150 years on, terrariums are once again making a name for themselves as one of the most on-trend horticultural hobbies.
Containers
You can be as creative as you like with your terrarium container, just as long as it is transparent. Glass is favoured by terrarium enthusiasts, and you can pick up all manner of weird and wonderful-shaped jars from flea markets and second-hand shops. There are also plenty of purpose-built terrariums in a range of shapes and sizes available in nurseries, garden centres, and online.
If your chosen container is oddly-shaped or has a narrow opening, you may need to use chopsticks or other tools to place and maintain your plants. Avoid coloured glass containers, as these will reduce the light available to your plants, and will obscure your view of them.
Closed Vs Open Terrarium
There are two types of terrarium; closed and open; each with very different growing conditions and requirements. Closed terrariums are usually sealed, creating an isolated microclimate and ecosystem within the container. Open terrariums aren’t sealed so are open to external conditions. What type of terrarium you have will depend on the kinds of plants you want to grow inside it. Closed terrariums are best for humidity and warmth-loving tropical plants, whilst open terrariums are best for arid, drought-loving plants.
What is a Closed Terrarium?
Closed terrariums are sealed with a removable lid. The enclosed container creates a miniature ecosystem that mimics tropical rainforest conditions. The plants and soil release water vapour and soak up nutrients from decaying matter, which is recycled, reabsorbed, and released in an almost infinite cycle.
How to care for a Closed Terrarium
The self-sufficient nature of a closed terrarium means they are perfect if you don’t want to spend time on laborious watering and maintenance routines and just want to enjoy your beautiful indoor garden. Once the terrarium becomes established, the ecosystem should maintain itself with minimal intervention.
Water
You will need to water your terrarium when you first set it up to initiate the cycle of the ecosystem. You should always use rainwater or de-ionised water, as terrarium plants can be fragile and the chemicals in water can upset the delicate bacterial balance in the container. Alternatively, leave tap water to sit for 24 hours before watering to allow the chlorine to evaporate.
Once established, you will rarely need to water a closed terrarium. Every few weeks you should test the moisture levels by dipping your finger into the soil. If it feels very dry, add a little water. If it feels oversaturated, leave the lid off for a short time to stimulate air circulation. You can reduce watering in the winter months when the plants aren’t actively growing.
Additionally, you can monitor the moisture levels in your closed terrarium by observing condensation collecting on the glass. It’s normal to see some water droplets collecting on the inside. If there are no water droplets, then the plants are too dry. If there is so much condensation that you can’t see through the glass, then your plants are too wet.
Remember to replace the lid as quickly as possible after performing any maintenance to prevent the terrarium from drying out, although you might want to open the lid for a short period every so often to allow a little fresh air to circulate.
Light
Terrarium plants don’t like direct sun, since the glass acts as a greenhouse. Too much sunlight will scorch the plants and cause the jar to dry out quickly. Instead, place your terrarium somewhere it will receive plenty of bright but indirect light. A north-facing windowsill or a south-facing windowsill shielded by a voile are good positions.
Closed terrariums can thrive under artificial lighting too! LED or fluorescent lighting will be more than adequate for the plants to perform photosynthesis without generating unnecessary heat.
If your plants start to become leggy or spindly, it’s a sign that the light levels are too low. You should rotate your terrarium regularly to ensure that light is evenly distributed amongst the plants.
Soil
Closed terrariums need layers to create adequate drainage and maintain a healthy ecosystem. Start with a layer of gravel so that excess water can drain freely.
Then add a layer of activated charcoal which will keep the ecosystem clean and prevent diseases and fungus by stopping the water from becoming stagnant.
Finally, add a generous layer of good quality, well-draining, fertile potting mixture. This should be deep enough to accommodate the roots of your chosen plants, with plenty of room to spread. The organic matter in the soil will decay over time, supporting microbial functions and releasing nutrients that are taken up by the plants.
Food
Once a healthy balance has been established in your closed terrarium, the plants will gain all the nutrients they need from the decomposition of plant matter and the potting mix, so you shouldn’t add any extra fertiliser to your terrarium.
What is an Open Terrarium
Open terrariums are never sealed, so don’t create a microclimate as closed ones do. The conditions in your open terrarium will be pretty much the same as the conditions of your house in general, meaning more flexibility in terms of planting choices, as any plant which would survive in your home will survive in your open terrarium. Open terrariums aren’t self-sustaining, so they will require the same level of care as normal houseplants.
How to care for an Open Terrarium
Water
Allow the contents of your open terrarium to dictate the frequency of watering. If your terrarium contains only arid plants, then water sparingly and infrequently. If you display vining plants like Pothos in your open terrarium then you will need to water more regularly.
Light
Sun-tolerant plants tend to flourish in the dry conditions of an open terrarium, so can be placed in south-facing windows and sunny spots. Cacti and succulents will need a few hours of sunlight per day, and the more sun they receive, the more likely they are to produce flowers. If you choose to display standard houseplants in your open terrarium, you should place them somewhere that meets their light requirements.
Soil
You can use any substrate you like in an open terrarium. Keep in mind that many open terrarium plants tend to enjoy drier conditions, so add plenty of drainage material such as sand, coco coir, perlite, or vermiculite.
Food
You should feed open terrarium plants as you would standard houseplants. They won’t generate their own nutrients since there is no ecosystem in place.
How to Plant your Terrarium
Whether you opt for a closed or open terrarium, create an intriguing and dynamic display by selecting diverse plants with a variety of colours, textures, and shapes. Terrariums containing only one type of plant can look a bit uninspiring.
Be mindful of the size of your container when selecting plants. If your terrarium is housed in a mason jar, don’t try to fill it with Monstera as they will soon outgrow it! Opt for plants with similar light and moisture requirements as this will make maintenance much easier. Faster growing species may block the light of other smaller species, so consider this this when positioning your plants.
Best plants for a Closed Terrarium
Closed terrariums are perfect for growing tropical, humidity-loving plants that might otherwise struggle in normal, dry household air.
In a closed terrarium, opt for low-maintenance plants with slower, more compact growth habits so you won’t need to open up the container for regular pruning, as this can disrupt the balance of the ecosystem. Similarly, if your container is awkwardly shaped it can be tricky to carry out regular pruning.
When positioning your plants, make sure none of the foliage is in contact with the glass as this can lead to fungal infections if the leaves are constantly moist from the water droplets inside the glass. Prune any plants which grow too close to the glass.
Baby’s Tears are an excellent sprawling ground cover plant for a closed terrarium. Their delicate circular leaves creep across the soil, adding plenty of texture to your display.
Ferns LOVE moisture and will thrive in a closed terrarium. They are also very tolerant of darkness, so won’t compete with other plants for light. Some ferns have vigorous growth habits though, so you may need to prune them regularly if they become unruly. There are hundreds of varieties to suit any size or theme of terrarium.
Heartleaf Philodendron is a sprawling vining plant, whose vivid green leaves are shaped like delicate hearts. Its love of warm, humid conditions mean it is quite content in a closed terrarium.
Mosses of all kinds need plenty of moisture to flourish. They provide a great ground cover to disguise the soil in your terrarium, as well as being extremely beneficial for the ecosystem. Moss is also a good indicator of the moisture levels in your terrarium. If it looks like it’s drying out, then it’s time to water. Like ferns, there are hundreds of moss varieties to choose from.
Satin Pothos is a slow-growing vine, so it doesn’t require too much pruning, whilst its unique silver-speckled foliage will stand out against other plants. Make sure its leaves don’t rest against the glass, as they are susceptible to fungal infections.
Fittonia are known as ‘nerve plants’ because of the vivid vein-like patterns which adorn their leaves. Their slow growth habit and humidity-loving nature make them ideal for a closed terrarium.
Best plants for an Open Terrarium
Whereas closed terrariums are a haven for tropical, moisture-loving plants, open terrariums are a paradise for arid, drought-loving plants like succulents and cacti. Air plants also thrive in the dry conditions of an open terrarium, and are especially good air purifiers too! Arid plants have the added bonus of being generally very slow-growing, requiring little to no pruning at all!
In open terrariums, you are less constrained by your container size, as more vigorous plants can out-grow the container through the opening. Vining plants, for example, look great trailing out of wall-mounted open terrariums.
Aloe is a sun-loving succulent that thrives in arid conditions. Their gel-like innards are also great for soothing wounds and burns, so are practical as well as pretty.
Bulbosa is a truly unique air plant with spindly tendril-like protrusions which emerge from its bulbous root base.
Jade is one of the most beloved of succulents, characterised by thick stems and dense leaves. It’s also known as the ‘lucky plant’, so placing a Jade in your open terrarium may just bring you good fortune!
Tectorum is another unique air plant. Native to the mountains of Ecuador and Peru, its short, fuzz-covered spines and small size give it a very cute appearance.
Sempervivum is a delightful cactus, also known as ‘Hens and Chicks’. It is prized for its concentrically positioned leaves which are reminiscent of a rose.
Xerographica is a slow-growing air plant with showy, curled bracts which make for a stunning display in a desert terrarium.
Best Plants for Small Terrariums
Your terrarium may be small, but it can still make a huge impact with these mighty miniatures!
African Violets are ideal for a small closed terrarium. Their vivid blooms add a stunning splash of colour whilst their compact size makes them easily manageable.
Haworthia fasciata is also known as the ‘Zebra cactus’ because of the white stripes which cut across its spiky, succulent leaves. It’s very slow-growing, making it perfect for a small open terrarium.
Pincushion Catci are spike encrusted succulents that are perfect for a compact open terrarium. Don’t be fooled by their tiny size though, these cute cacti are sharp to touch!
Sungonanthus Chryanthus, also known as the Mikado plant is a unique, delicate plant with tiny, single white flowers perched atop dainty, slender spikes. Native to Brazilian swamps, this slow-growing plant is perfect for a small closed terrarium.
Venus Fly Traps are humidity-loving carnivorous plants that are sure to bring more than a hint of drama to your small closed terrarium, despite rarely exceeding a few inches in size!
Best Plants for Large Terrariums
The planting possibilities are almost endless if your terrarium is blessed with an abundance of space. Here are some of the best plants for large terrariums!
Oxalis are humidity-loving plants ideal for larger closed terrariums. They have a sprawling growth habit with large, triangular leaves in a stunning shade of deep purple.
Peperomia is a classic choice for larger terrariums, with their sizeable lily pad-like leaves and bright green hue. There are over 1000 species of peperomia to choose from, including the much-loved Chinese Money Plant!
Prayer Plants are a fascinating, animated addition! Its large leaves are decorated with a beautifully stylistic variegation pattern and will turn themselves upwards at night as if they are praying.
Wandering Jew plants are prized for their shimmering, deep purple foliage. Their creeping, vining growth habit means they like plenty of space to spread out in a generous terrarium.
FAQs
Why is my glass foggy?
If the glass on your closed terrarium is becoming foggy, it’s a sign that it has been overwatered and moisture levels are too high. You should leave the lid off for a short time to allow the plants and soil to dry out a little.
Why are there insects in my terrarium?
Some insects, such as springtails, are a natural and healthy part of the ecosystem of your terrarium, aiding with decomposition and eating mould. You should inspect your terrarium regularly for signs of more malignant pests such as aphids or mealybugs, who may have been introduced whilst the lid was off, and will quickly wreak havoc on your plants if allowed to populate.
What are the Common Problems to Look Out For?
Root rot – Plants are more susceptible to root rot when they are in a consistently wet environment like a closed terrarium. To prevent root rot, leave the lid off your terrarium for an hour or two every so often to allow fresh air to circulate, and avoid overwatering. Look out for yellowing or wilting foliage, as these are usually the first symptoms.
Fungus – Fungal diseases and mould thrive in warm, moist environments with minimal ventilation. Leave the lid off the terrarium for a short time after watering to prevent spores from developing. You should also try to avoid misting your plants as this can encourage fungal infections when the foliage is moist. If you notice a large build-up of decaying matter or debris on the bottom of the tank, it’s best to remove it as this can harbour mould. Similarly, remove any plants that look unhealthy as they may spread disease to the whole terrarium. If you notice white, fuzzy mould appearing on the substrate you should wipe it away quickly and ventilate the terrarium for a couple of hours. You could also sprinkle a little baking soda over the substrate to kill the mould without harming the plants.
How long will my terrarium last?
Open terrariums can last for many years, depending on what you plant in them, so long as their needs are met and they aren’t plagued with pests or disease. Cacti can have particularly long life spans, and houseplants can live for several years.
You may need to replace the odd plant along the way as they reach the end of their life, but a closed terrarium can last indefinitely once established, as long as the healthy balance of the ecosystem is maintained.
Now you’ve read our ultimate guide to creating and maintaining terrariums, you’re all set to get building your own tiny ecosystem, and enjoy its enchanting, dynamic beauty for many years to come!
