Terrarium Guide

Your One-Stop Terrarium Guide: All You Need to Know

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Like the idea of some greenery but lack the garden space? Want a self-contained garden so you have a better chance of plant life instead of death in a dome?

All you need to set yourself up with a thriving ecosystem under a glass container is right here. The tools you need, the stuff to use and the most pressing questions answered.

You’ll even find a video by Martha Stewart near the end of the article showing you how to make your own really practical tools for building your terrarium – the easy way.

Your One-Stop Terrarium Guide All You Need to Know

Before you dig in, it helps to understand the inner workings – or the science behind the mystery…

How Terrariums Came to Be (Historians call this history)

The first ever terrarium to be built was back in the 19th Century and was put together with only two precise design features as part of an experiment brought about by an accidental discovery related to the pupa of a moth.

Who’d of thunk it?

It’s true. It was actually an Entomologist (Dr. Nathaniel Ward) who dropped the pupa of a moth into a sealed glass jar and found that after a while, the soil base started to grow a fern and some grass.

Low and behold, curiosity set in. Why? Why on earth was plant life being found in an enclosed space with nothing to feed and nourish the plants?

That set way to the first custom built case to find out how long plants could survive in this closed climate.

The first design was constructed by a carpenter with only a couple of important specifications.

  1. To use the hardest of woods so the case would resist any decay from the condensation from the moisture inside the container.
  2. To have the joints be solid for an airtight seal between the glass and the wood frame.

For the be-all-and-end-all of scientific studies, two custom built containers were filled with a variety of grasses and ferns native to Britain, then loaded onto a cargo ship to set sail across the high seas to Sydney, Australia – a 6-month sea voyage.

Six-months later, the two containers were unloaded at Sydney Harbour, every plant thriving, no additional nourishment needed. For indisputable, conclusive findings on a study though, a return journey was needed.

Prior to this voyage, it wasn’t possible to ship native plant species across borders. This is why the first terrariums made history and why Dr. Ward went down in history as a plant biologist and not an entomologist.

For the return shipment, the cases were cleaned out and the grasses and ferns native to Australia were loaded into the Wardian Cases. The return sea journey took 8-months and a battering due to the stormy weather. The ship went through horrendous abuse, yet there was no harm to the plants when they arrived in London in February of 1835.

The trial shipment was successful and Ward went onto publish the exact details of how this was possible in a book titled “On the Growth of Plants in Closely Glazed Spaces” in 1842.

Just so you don’t waste your money on historical books… Books published before 1923 fall into the public domain meaning their free to all. Otherwise, the rule of thumb for copyright works is 70 years after the death of the author.

For books in the public domain, Google digitizes them where possible and releases them in the Google Play Store books collection for reading on Web enabled devices like your PC or tablet.

You can get a free copy at Google Books.

No need to pay astronomical prices on Amazon, Abebooks or any other platform where authors reproduce these historical works.

With that out the way, let’s dive into the specifics of terrariums…

Terrariums Defined

Terrariums are glass enclosed containers. Think bottle gardening but on a broader spectrum because so long as the container has glass sides, it’ll work wonders to build your own mini-garden.

Think of it like a miniature greenhouse you can park on a shelf, a bookcase, windowsill or any area of your home to have a beautiful indoor miniature garden.

Small Closed Terrariums

There are two types of terrariums you can buy or build, although technically speaking, one’s not even a terrarium. Nevertheless, sellers call them either:

  • A closed terrarium
  • An open terrarium

Now, the open terrarium’s ludicrous because it’s against what a terrarium is. The Latin definition of the word ‘Terrarium” means enclosed earth – Terra, being Latin for Earth and arium being adapted from aquarium for the enclosure part.

Suffice to say, an open terrarium is just a bowl. Or a bottle of Coke cut in half and used as an open top container. Whatever works. 😉

The type you use will be determined by the types of plants you’re planting and whether they prefer lots of air or high humidity.

A closed terrarium, (as in a real one) is best for plants that thrive in humid environments, whereas, an open top container is best for succulents as they prefer air flow over humidity.

What you can’t do is mix and match different types of plants to your liking because you need to plant your plants based on the environment they prefer.

You’ll understand that better when you know…

How the Ecosystem of Terrariums Work

Terrariums are one of those gardening projects the kids won’t get bored with and they’ll learn how an ecosystem works. You can watch the whole process unfurl before your very eyes.

The idea is simple. In a closed terrarium, there’s a high level of humidity. When water and humidity are in the same zone, condensation happens. You can see that on the container walls.

Closed Terrarium

As the condensation rises, it trickles back down to water the plants, so the water is being recycled. The bonus here is you don’t have to water the plants as frequently, or if it’s really humid, it’ll be self-sufficient and water itself.

Another side effect of the closed terrarium is the water will go through two stages by passing between liquid form and gas.

In terms of how the plants use that ecosystem to live, they get all the nourishment needed for photosynthesis (light dependent), watering and oxygen. The moisture content will return from the walls of the terrarium to the soil where it’ll then replenish plant roots to keep it nourished, growing and strong.

Large Closed Terrarium

It’s not all plain sailing though. Terrariums need a bit of planning so you get the right types of plants, the ideal size of container for them and the base layers just right for sufficient growth and plant longevity.

The starting point for a self-sufficient terrarium is to decide on the types of plants you intend to grow. Keep in mind that terrariums are glass enclosures and glass filters UV rays. So, terrariums aren’t suited to sun-loving plants. The ones that prefer shade do best. Direct light won’t work as a replacement for sunlight either because that would just heat the terrarium up too much.

Below you’ll find lists of plants suited to both open and closed terrariums. When deciding on which ones you want to give a try, mix and match your plants from one list only.

What not to do is take one from the open terrarium plant list and put it together with a plant type suited to a closed terrarium. If you do that, what will happen is the plant suited to the open enclosure will wind up too moist if it’s put in a closed terrarium and the one or more suited to a closed enclosure would wind up too dry.

Make sense?

The only other thing you need to pay attention to when picking plants is the size they expect to grow to. Botanist, James Wong recommends a minimum terrarium size of 30 cm by 30 cm. That’s a minimum though and once you see what you need to include as the base layers for a proper functioning terrarium ecosystem, you may want to consider going larger and wider.

As far as the types plants to grow, you can either go all succulents for an open terrarium or all humid-thriving plants that do better in closed terrariums. Remember: You can’t have both because in an open terrarium, it can be too dry, the other too wet. You need to mix your plants based on the growing environment they do best at.

With those points in mind, check out these…

Closed Terrarium Plants

For a closed terrarium (one with a lid on it) you need humid loving plants.

Terrarium Close Up

A List of Plants Suited to Closed Terrariums

  • Rex Begonia
  • Pothos
  • Aluminum Plant
  • Button Fern
  • Baby Tears
  • Mini English Ivy
  • Maidenhair Fern
  • Artillery Fern
  • Hypoestes (polka dot plants)
  • Friendship Plant
  • Starfish Plant
  • Aquamarine
  • The Silver Nerve Plant

While all humidity loving plants do well in closed terrariums, you should monitor the level of condensation. If it starts to show loads of condensation building up around the sides and seals, take the lid off it and let it air for a short time to reduce the moisture content. That will prevent the plants from becoming over-watered, which is the most common causes of terrarium failures.

What to remember with closed terrariums is that inside the container is a self-sustaining ecosystem that keeps the plants alive. But, while it should be self-sufficient, sometimes, depending on the conditions around your home, a little intervention is required to keep the moisture levels at a reasonable level.

Open Terrarium Plants

Succulents are the best type of plant to use in an open terrarium. They thrive in open air and are super easy to care for, requiring just a misting of water to keep them nourished.

Planting an Open Terrarium

A List of Plants Suited to Open Containers include:

  • Echeveria Blue Sky
  • Red Tip Hens & Chicks
  • Whale’s Tongue Agave
  • Burrito Tail
  • Crown of Thorns
  • Feather Cactus
  • The Flaming Katy Plant
  • Zebra Haworthia
  • Roseum
  • The Stone Crop
  • Moon Cacti
  • Dudleya
  • The Black Rose (Zwartkop)

In addition, Crotons are spectacular for brightening up an open terrarium. The leaves are shiny, super thick and always have bright colored leaves.

Furthermore, if you want to dive deeper into specialty terrariums, there’s a handy fact sheet put together by Cornell University’s Cooperative Extension listing plant types for woodland terrariums, tropical terrariums, and more succulents and cacti plants you can grow in open terrariums. That report’s here.

Now comes the real stuff…

The Necessities for a Proper Functioning Terrarium

The base of a terrarium always begins with a layer of gravel, rocks or pebbles.

There’s a reason you need these. Actually, there’s two: drainage and aeration. What happens with the rocks, pebbles or gravel is they’ll absorb the water content and then as it evaporates because of the higher temperatures, the water will vaporize helping to air the plants. An inch or two of pebbles, rocks or gravel will do the job.

Then…

Add Activated Charcoal

For closed terrariums, always add a half inch layer of activated charcoal. You’ll be able to pick this up at your gardening center, or use Hoffman’s Horticultural Charcoal (link to Amazon).

Charcoal

The reason you ought to use this (the activated charcoal, not specifically that brand), especially with closed terrariums, is because odors build up to the point where it’ll eventually start stinking.

Harmful bacteria and other impurities will wreak havoc on the soil preventing your plants from getting the nourishment they need. And it’ll help with the water absorption, retention and redistribution of the water inside the terrarium. All of which will be essentially deodorized releasing only the water that’s been purified, with the toxins sanitized to keep the environment healthy for the plants.

In effect, it’s an integrated filter system to purify the air and water. Don’t build your terrarium (open or closed) without this layer of activated charcoal. Some guides tell you it’s optional. It’s not!

Then…

Add Some Sphagnum Moss

This is going to help even more with the water retention. And as it turns out, it’s popular with bushcrafters because it can do loads of stuff beyond moisture retention…

Check what this guy has to say on it (and notice the amount of water that pours out of the moss as he squeezes it).

One thing that can’t be ignored is this rule: Don’t use moss (or any plants) you find in the forest, parks or private land. It’s illegal in most countries and that’s for environmental protection. There are loads of videos and guides that say you can just go outdoors and collect what you want at will. That you can, but you can also get a hefty fine if you break bye-laws in place to protect natural habitats.

In the U.S, it’s possible to get a permit at a USDA Forest Service District Office – fees apply – and you need to meet the criteria. You won’t be able to pick at will because it has to be low impact and low value forestry products.

The simplest way to get the stuff you need for a terrarium is just to buy it from a garden center or an online supplier.

Going back the sphagnum moss, there’s another reason to use this. It’s an additional layer that’s going to prevent the potting soil from mixing through the base layer of gravel, which can be the cause of mold developing.

Once that’s done…

Add the Right Mix for the Topsoil

The last part is the topsoil and it’s equally as important to get right than every other layer. You can’t take soil from your garden and expect it to work in a terrarium.

The best soils for terrariums are a triple mix.

Now, depending where you are, triple mix may mean different things, so here’s what’s meant by a good triple mix:

  • 1/3rd Peat Moss
  • 1/3rd Sand
  • 1/3rd Soil

This is uber important because this type of soil gives you added aeration and moisture retention, especially when the soil has peat moss because that’s dead sphagnum moss and it still has great moisture retention.

With this type of terrarium setup, you’ll be all set to plant a variety of plants in your terrarium and they’ll all do well.

In terms of size, the minimum mentioned earlier was 30 cm by 30 cm. By this stage, you know what you need to house in your terrarium before you even consider the plants you’re going to grow in it so you’re likely thinking space-wise, it’s going to get compact fast.

So, think about your terrarium size and what you plan to grow before you buy one. That’ll avoid disappointment and having to start over.

To recap what you need as your terrarium base layers:

  • Roughly 2-inches of gravel, stones, rocks or pebbles (colors to suit your preference)
  • Followed by a half inch of activated charcoal
  • Then a couple inches of sphagnum moss
  • The top soil should be 1/5th of the terrarium size. For a terrarium of 30cm by 30cm, you’d be looking at 6cm of potting soil – roughly 2.5-inches.

The total size of those combined would take up roughly 7-inches. As most miniature plants can grow to 12-inches tall (30 cm), it’s clear to see the 30 cm x 30 cm may not be quite the right size although it is determined by the type of plant you put in it. If you stick with dwarf plants, you would get away with a 12” x 12” terrarium.

With the necessities taken care of, then comes the creative part of…

Decorating Your Terrarium

Now comes the fun part. However, before that, you should know that not everything in a terrarium has to be plants. In fact, you don’t even need to grow plants in them if you don’t want to. Terrariums can be just as appealing and decorative with zero plants grown in them, albeit, you’ll miss the functional aspect of the ecosystem.

Decorated Small Terrarium

Here’s some ideas to get your creative juices flowing

  • Add miniature figurines – Disney if you like. Smurfs, dwarfs or trolls… anything goes. Stick some trolls under a bridge if you like. You’ll find plenty of aquarium decorations in pet stores and from reptile suppliers.
  • A teeny piece of bark wood to attach a succulent plant or more too
  • Pine cones
  • LED candles or fairy-lights – provided they’re battery-operated and not electrical due to the high moisture content
  • If you want to add a time element, take the clock face off an old watch and pop that inside the display
  • Marbles can add a bit of shine to the design
  • Seashells could be a good addition for a bathroom terrarium
  • Miniature animals like those you get in kids play sets. Drop in some sheep, cows, bulls or horses. Maybe even a row on tiny ducklings. I even added dinosaurs to my mini succulent terrariums
  • Feathers, or add a dream catcher if that’s your thing

Make them mystical, bright, creative or just let your plants add the color element into your show.

There’s no design rules for terrariums. The whole idea of building a terrarium is in part to be creative while getting the benefit of an indoor garden that’s self-sustaining, requiring little to no intervention and certainly no drilling shelves or the likes to display them. They do well in any area of the home, requiring only a little light and indirect light at that.
Let your imagination run wild, plot your design and go for it. Nothing’s ever final as you can always redesign a terrarium to mix things up so you’re never bored with the same old.
Got Questions?

Your FAQs Answered

Where can you position your terrarium?

The positioning of your terrarium is important for the plants to get the growing climate they need. The ecosystem inside the terrarium will take care of the plants, but you still have to make sure there’s enough light to allow for photosynthesis to happen or the plants won’t grow as well as they should.

Whether you’re putting your terrarium in your home or office, the only thing to remember is they don’t do great in direct sunlight, preferring plenty of artificial light. Keeping them out of direct sunlight will prevent the terrarium from overheating, which would cause leaf burn on the plants in the terrarium.

That being said, using artificial lighting still can give them too much heat, so keep the indirect lighting at a distance, but still enough for the beams to reach the plants without raising the temperature too much.

Is it possible to over-water a terrarium?

Yes. It is possible and the simplest way to prevent it from happening is to keep an eye on the moisture content. If you see the water building up against the glass walls and basically dripping consistently, it’s time to lower that slightly.

Terrariums

Just take the lid off it and let it air for a few hours, then seal it again. That’s if it’s a closed terrarium. If it’s an open terrarium, the only way you’ll over-water it is manually by watering it too much, using a watering can instead of a mister.

Open terrariums only need a light misting on occasion. Roughly once a week.

For a closed terrarium, you should be able to get by for a couple of months with it maintaining it’s own watering system. When you notice it start to dry up, you can use a mister to give it a quick spray, or just add a spoonful or two of water into the container, or even use a teeny eyedropper to drop a few squirts of water into the terrarium.

What about pruning?

Yup, this should be done.

Pruning the plants in the terrarium is important because if you let them grow too long/large, they could outgrow the container, but more importantly, they may not be getting the right amount of nourishment from the couple of inches of soil they have for the roots. And the larger the plant grows, the larger the root system becomes. That’s going to cause the roots to compact, restricting air circulation. That will eventually cause damage to the roots and cause problems with your plants.

Keep them trimmed and when you notice them getting large, gently tug them from the soil and check the roots aren’t constricted. If they have become too compact, you may need to put the plant in a larger container suitable for its size, or swap it out for a new plant that’s the right size for the terrarium.

How You’ll Know When to Water or Air Your Terrarium

The soil in a terrarium should be dry before it’s watered. You can easily check that by touching the top soil. If it’s dry to the touch, it needs watered. If not, it won’t.

Can it get too wet in there?

Yes it can. If you notice the walls on your terrarium are completely fogged, you have a looming problem that needs to be addressed before plant rot sets in. Too much moisture in a terrarium is the biggest cause of them ultimately breaking down and all the plants in it dying.

The easiest fix for a closed terrarium is to leave the lid off of it until it cools. Moving it to somewhere temporary with better airflow such as on a windowsill with the window open, or in the hallway with the door open to increase airflow will let it air faster. Then just put the lid back on it when the condensation dies down enough.

This shouldn’t happen often and generally will when the season changes from winter to spring. Otherwise, it’ll be a temperature issue in your home, such as having the lighting too close to the terrarium, or sitting it beside or above a heater.

The heat inside the terrarium is a natural side effect of the container being closed, or compact. Not as a result of deliberately placing the terrarium near a heat source to increase the humidity. Let the terrarium do the work it’s designed to do.

If on the other hand, you’re seeing no condensation at all, it’s the opposite that’s happening. There’s not enough moisture in the terrarium to cause the rain cycle – when the water soaks through the soil, reaches the pebbles, evaporates and condenses up the walls and then drips back down on the plants – just as would happen in a rainforest’s climate. That’s the ecosystem you’re creating and it’s the reason for closed terrariums.

Open terrariums are a different breed and technically aren’t terrariums at all because by definition (or Latin definition anyway), a terrarium means “enclosed earth.” Open isn’t enclosed, so the plants will need misting more frequently. Closed terrariums need watered infrequently and it’s more about monitoring condensation levels to make sure it’s not too moist causing the plants to drown.

Buyer’s Guide

Surprisingly, you can buy a terrarium from a variety of places. It’s not just garden centers that sell high quality terrariums, despite them being used for plants. They serve multiple purposes. Interior design stores will sell them, you’ll likely be able to spot them in independent home and lifestyle stores, and on pet supplies websites, especially those specializing in reptile, snake supplies and aquatics.

There’s also specialist retailers selling complete terrarium kits, DIY terrariums, geometric designs and ones designed to be hung.

Here’s what you ought to know before you hit the aisles – or speed browse Google images for cool looking terrariums to build.

Size

The size of terrarium you need will be dictated by the type of plants you intend to put in them. If you’re going to grow a plant that can grow to 46 cm, you’ll need a terrarium tall enough to accommodate plant growth. Remember to add the 5.5 inches for the base and then whatever the total height of the container is, divide that by five because 20% of the terrarium volume should be the topsoil.

The rest of the layers stay the same.

Open or closed

This is, again, based on the types of plants you want to grow. For succulents, it’s a succulent terrarium to buy which will be open-topped.

High humidity plants will need a closed terrarium.

Shape

Think of where you’re going to put your terrarium in your home to help decide on the shape that’ll work best.

Hanging Terrariums

Some choices include:

  • Geometric shaped terrariums
  • Asymmetrical glass containers
  • Hanging terrariums
  • Or just plain old glass jars – open or closed lidded
  • There’s also glass cloches, which are like little glass domes that you pop your mini garden inside

The only shape never to buy is a pyramid. It wouldn’t water evenly because of the pointed top.

The size of the opening

This is the most overlooked part of buying a terrarium. The size of the opening needs to be large enough for you to get your hand in and work your creativity to arrange everything how you want it.

Tools to Help You Set Up Your Terrarium

Pruners

You’ll need a good pair of pruners to keep your plants trim and proper. They’ll need to be sharp enough to snip off dead leaves without ripping them. You want a clean cut with sharp blades every time, otherwise rips on the leaves and stems can leave your plants open to plant diseases.

A funnel

Because you’ll have a mighty hard time getting your layers into the container without one.

A spray bottle

Any mister will do, so long as you clean it out before using it.

Long tweezers

These are handy for reaching into narrower topped containers and moving your miniature plants and the layers to get your arrangement just right.

Using Tweezers In Terrarium

You can even make your own terrarium tools. This video by Martha Stewart shows how to make your own practical tools that are ideal for working with terrariums.

Your One-Stop Terrarium Guide: All You Need to Know was last modified: August 9th, 2019 by The Practical Planter

Comments

  1. great,i have 3 large aquariums as i’ve fish kept for years but i’ve grown bored,this looks exciting..thanks.

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