Everyone appreciates an open terrarium, or as I like to call them – bowls of plants.
Just kidding. They may not be a terrarium in the truest sense of the word, but there’s still a place in my heart for all botanical creations.
Generally speaking, open terrariums are much simpler than functional closed terrariums – making them a versatile choice for the home.
But they do still have their own unique requirements. If you plant your succulents like you do your ferns, you’re going to have a problem.
So, in this article, you’ll learn when to plant an open terrarium vs. a closed terrarium. Which plants to choose, and how to build and care for your open terrarium.
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Why Make an Open Terrarium?
Open terrariums are popular, and for good reason.
They’re a great way for people to get started with terrariums, and I’m 100% behind that. You still get all the experience of planting and building a terrarium, but you don’t have to deal with many of the factors that can easily go wrong in a closed system.
You could argue they’re more ornamental than technical, but they come with plenty of direct advantages:
- Better airflow for plants.
- No condensation issues.
- Lower risk of mold and rot.
- More forgiving, with a higher chance of success.
But, what you gain in simplicity, you lose in utility.
When to Make an Open vs Closed Terrarium
To open, or not to open – that is the question.
Though, in reality, it’s an easy one to answer.
If your plants like moisture and humidity, you need a closed terrarium. If your plants don’t, you need an open terrarium.
Sounds pretty simple (and it is), but there’s a lot of room for experimentation within that, and there are still versatile plants that can do fine in both.
So, let’s take a closer look.
Best Open Terrarium Plants
There are two directions you can go in, and there’s pretty much no room to mix and match. The first is the more obvious, and the second breaks the rules a tiny bit…
1. Arid Plants
This is the classic open terrarium aesthetic.
Succulents, cacti, and air plants are perfectly suited to life in open terrariums.
(Essentially plants that don’t like without humidity and consistent moisture).
They have similar care requirements, so it’s easy to put them together in an interesting mix of textures and shapes.
Air plants from the Tillandsia genus are a varied, beautiful, and easy addition.
However, you’re not limited to arid plants (even if Pinterest suggests otherwise).
We don’t have to cater to the extremes; there’s a lot of grey area between desert and jungle plants.
Remember, an indoor open terrarium has the same environmental conditions as your house. If your houseplants are thriving in a pot on the windowsill, they’ll most likely be just fine in an open terrarium too.
There are lots of houseplants that I’d love to put in closed terrariums, but realistically, they’ll grow too big and burst out the top.
Not a problem for open terrariums…
👉 Check out my Ultimate Terrarium Plant Guide for more info.
Can You Grow Moss in an Open Terrarium?
If you frequent Pinterest, you’ve probably seen open terrariums with tropical mosses.
Lush, wavy tufts of moss nestled between succulents looks good, sure. But I can guarantee they didn’t last longer than a week…
Pairing arid plants with moisture-loving moss is like storing your ice cream on top of your radiator, two very different worlds.
👉 See the wide range of preserved moss here on Etsy.
*This does come with a small caveat: preserved moss can’t get wet as chemicals and dyes can leech into the design, so you’ll need to remove it when you water your piece and add it when the topsoil is dry again.
Open Terrarium Layers
The composition of your terrarium layers will be relatively similar no matter which kind of build you go for.
- Drainage layer – Whether you’re using arid plants (e.g., a cactus terrarium) or houseplants, good drainage is essential to prevent root rot. A drainage layer of leca balls or lava rock, covered with a substrate mesh still works well for open terrairums.
Charcoal layer– Mold isn’t an issue for open builds, so the filtration properties of charcoal are relatively useless here. Save your pennies and skip this step.
- Substrate/soil layer – As you know, drainage is very important for open terrariums (as is root aeration), but how that translates to soil depends on your plants. Aroid houseplants will need a light tropical plant mix with elements such as orchid bark (our tropical terrarium mix is a good fit), and arid plants need a gritty succulent and cacti mix with elements like sand and pumice.
Open Terrarium Care
To be honest, there’s no super strict science to open terrarium care.
Without the need to finely balance a tiny ecosystem, you’re essentially just trying to keep your plants fed and happy. It’s no different to looking after your houseplants, but often that’s hard enough, right?
So, if you’re used to keeping succulents or houseplants in pots around the house, you can usually treat your open terrariums in much the same way.
Seeing as open terrariums have no natural water cycle, it’s going to fall to you to keep it topped up. Sorry!
Watering requirements and methods will vary with your plants.
Succulents have their own watering preferences. Experts advise that they like to have their roots soaked with water but then be allowed to dry out again for a few days. So, unlike closed tropical terrariums, misting isn’t recommended.
That said, pouring water isn’t a good idea either. Not only is it likely to disturb your careful planting, but a drainage layer is only going to go so far and isn’t as effective as a hole in a pot.
Where closed terrarium plants are almost all shade-loving plants, open terrarium plants are often the opposite.
Which means you can actually put these by the window and show them off – hurrah!
Succulents like to have several hours of direct sunlight a day, so they’re best placed on a windowsill where they’ll get some morning rays. Houseplants will vary.
Open terrariums are much more susceptible to bugs, pests, and infestations than their closed counterparts.
Sadly, mealy bugs and gnats have been the death of many noble houseplants, and you’ll need to be extra vigilant on that front.
So, if you see your plants rapidly declining, there’s a good chance it’s down to an insect of some sort.
Give them a good inspection, try to identify the little buggers causing the problem, and treat them accordingly – consistency is key. We use neem oil when we get pest outbreaks.
Terrariums containing houseplants and vines tend to quickly outgrow their vessels. Some intentional spillover can look great, but you might also have to trim a lot more aggressively than with closed terrariums.
Arid plants, on the other hand, will require almost no pruning… ever.
In an open system, things can get a little dusty.
I find that you can generally just buff the glass with a microfibre class to get it clean and shiny again. Though if it’s particularly dirty, you can wipe it with a wet cloth first (using distilled water so as to not leave calcium deposits on the glass).
The same goes for any particularly glossy succulents.
If you’re using top stones or gravel on top of your soil, a small brush is best to gently dust them off.
Over to You
I’m interested to hear how you feel about open terrariums.
Do you have any of your own, or maybe even prefer them? Maybe you’ve managed to grow some cool plants that other people haven’t?
👇 Let us know in the comments.
Need some inspiration for your next build? Check out our Terrarium Ideas post, or if you’re ready to join us on the dark side with a functional terrarium, check out our DIY Terrarium Guide and Essential Guide to Tropical Terrariums.