The Basics of Closed Jar Terrariums





Introduction: The Basics of Closed Jar Terrariums

Gardening Contest

Second Prize in the
Gardening Contest

I've been creating closed jar Terrariums for about a year.  It was something I wanted to learn and finally decided to give a try.  Since then I have picked up a lot of info about making Terrariums, and also teach workshops on making them.  The workshops give me motivation to learn more, hone my skills and work hard to get the best outcome for the groups that come through. 

This instructable will give you a guide to collecting and cultivating moss and making a closed jar Terrarium.  Make sure you read all of the notes on the images for extra info.

Step 1: Moss Gathering and Prep

Moss Gathering and Prep



*Plastic Bags
*Spray bottle
*Plastic Containers

When collecting moss to use in your closed Terrarium it is important to harvest the moss and cultivate it for approximately 2 weeks before putting the moss into your jar Terrarium. Cultivating it for two weeks lets you see what is does in closed environments. You can see how the moss will grow, weed out any mouldy spots that appear and see if the moss you have found is suitable for closed environments.

Finding Moss

We've had very wet weather in Brisbane recently, perfect for all the moss that has taken off over the last few years. I am pretty lucky that two yards near me have a good supply of moss along their front fence lines, so I often pick that. I also grab moss from other spots. We have a fair few different varieties of mosses in different spots. You can find moss in shady, moist spots, often near fence lines. It is very rarely under/around tree bases and any of the moss around the tree bases here is unsuitable for closed jar terrariums as it goes brown. Moss seems to enjoy some sun each day, so look for locations that enjoy just a little bit of sun.

The best way to find moss is go for a long and rambling walk with your eyes down, during or at the end of your rainy season. Take note of the moss patches in your area so you can come back to them. Even if the moss goes brown and looks dead you can bring it back to green quite quickly by harvesting and popping into containers.

I collect moss in clear freezer bags. I take the bags and a few sticks out with me and dig up clumps. It usually comes up in big clumps. The bags get full of a range of mosses from the area. When I get home I usually just dump it and come back to it sometime that day. No rush, it is perfectly fine in the bag for a day or two as long as you keep the bag closed.

Avoid moss that has gone to seed. When moss has gone to seed it will have little stalks with balls on the end. Do not collect this moss. It tends to go very brown, maybe even dead, and will not grow in a Terrarium. If you notice your moss grow little stalks pull it out and throw it in the garden.



Step 2: Preparing Moss

Preparing Moss in Containers

When I put the moss into containers I mix up the types and try not to break up the clumps too much. It is better to have large clumps that I can break up when setting up a Jar rather than have to put in a bunch of small clumps. I leave the soil that came up with the moss on the moss.

I have found it is essential to use containers approx 5-7cms tall. The moss does go “off” in shallower or deeper containers. I will explain a bit about this when we get to making the Terrarium.

When you put it into a container you may need to spray it if it is dry. It is better to under spray than over spray. I usually say two sprays with the sprayer and see how it goes. If you have a look at my photos you can see the level of condensation on the walls of the containers. The trick is to not over water as you get more mould. If moss is water logged it often gives up. Underspraying means your moss looks dry and crunchy.

Once the moss is in the containers I put the lid on and check the moss every few days and pull out mouldy or brown patches.

If the moss in the containers grows mould throw the mouldy bits out. If it goes brown throw it in the garden, it will probably come back to life in the right space in the garden but is not suitable for a closed environment.

You can also plant healthy moss in suitable spots in the garden to get more to grow!


Step 3: Putting Together a Jar Terrarium

 Putting Together a Jar Terrarium


*Glass Jar with a Lid
*Little Pebbles/gravel
*Activated Carbon/Charcoal

*a couple of paddlepop sticks (popsicle sticks?) are handy if you have a deep jar with a small hole.

These are the bare essentials. You really do need all of these. Here in Australia Activated Carbon is about $35 for 500grams, add shipping if you cannot source it locally. It sucks to have to pay that much but it is essential. The good news is that a 500gram bag will last you a really long time. To ease the blow you can always plan to make a few Terrariums or make them with a group of friends and split the bag between you.

Now that you have some good sturdy moss following my previous instructions you can put together your moss terrarium.



Step 4: Build Your Terrarium

 Build your Terrarium

1. Stones/pebbles/gravel
2. Charcoal
3. Netting
4. Moss and soil
5. Decorations and seeds

These are being built up in layers. The only layers you could mix together are the moss and soil and seeds.

For something a little different think about...

Add only a small patch or island of moss and use stones for the rest of the terrarium.

Make the ground undulating or sloped.

Add some seeds for some little plants in your terrarium

Add an animal (a plastic one)

Stones/gravel should be added to fill about 1/4 of the jar.
Charcoal/Carbon should be sprinkled on, about a teaspoon for a jar about 7cms diameter.
Netting, cut to size.  You don't want to see it from the side of the jar though.  You can give the jar a squirt of water onto the netting to prevent the soil falling through.
Soil, in a thin layer and to even out your moss height.   
Moss up your jar.  Add as little or much as you want.  I like to leave space under my animal if I am putting one in.
Add an animal and some seeds you've found if you'd like to grow some little seedlings.  The plants shouldn't grow very big.  I have found that they tend to grow to suit the closed environment they are in.


When your jar is done give it a squirt.  1-2 squirts at the end is usually enough.  If you think you've given it too much moisture you can take off the lid for a day or so.  It is really wet you can leave it in the sun, lid off, for a day.

When building a Terrarium they say the magic ratio is 1/3 filled and 2/3 space. I have found this to be about right. Terrariums with less or more space can grow okay, but I have found the 1/3 filled, 2/3 space ratio seems to work well. This probably has something to do with the amount of evaporation, air flow and how the moss feels in the environment.

Things to remember

There is the possibility that there will be eggs that may hatch in the soil or moss, if this happens pop the lid and let the little bugs out.

The soil and moss does have bacteria and miscroscopic animals, please wash hands after adding your moss.



Step 5: How to Display and Care for Your Terrarium.

How to display and care for your Terrarium

Moss terrariums should be sealed and only opened every now and then. Reasons to open may be; mould growing (from excessive moisture), looking too moist (look at the soil under the moss, does it look really sloppy and wet?), watering in the hot months, bugs hatching, having a closer look at your plants and to show your good work off.

I have found that it is generally unnecessary to water them unless you can see your soil looking dry or the walls of the terrarium are not misting up. It may be necessary to give a light spritz mid summer depending on how things look, or mid winter if your climate has a dry winter.

Your moss terrarium grows best in a well lit area that has NO DIRECT SUNLIGHT hitting the jar as this will burn and cook your plants. Rotate the jar for even growth of moss.

In case of emergency

Moss Terrariums can die, or start to look pretty horrible. You can always throw out the Insides of the terrarium, wash your decorations and make a fresh one.

If you spot mould early you can take off the lid and put the Terrarium in the sun to attempt to kill the mould. You need strong, full sun and will need to spray and replace the lid at the end of the day.


2 People Made This Project!


  • Paper Contest 2018

    Paper Contest 2018
  • Pocket-Sized Contest

    Pocket-Sized Contest
  • Science of Cooking

    Science of Cooking

We have a be nice policy.
Please be positive and constructive.


Just make sure if you put any insects or bugs look up what they need to survive


2 Questions


What plant would you recommend? If it were for a very humid climate.


Hi! Teaching a nature class and looking forward to the day we make these. I live in the US. What seedlings would you recommend to add? thanks!


I made this too! Let's see how it goes.


Don't put it too close to a window ! I had one bottle that exploded due to direct sunlight for a long time in hot days, and broken glass flew to 10m from where the bottle was, prefer using cork to seal soo they can pop up instead of gluing the plug like i did !

Can someone please advise if activate charcoal can be used in powdered form or is it absolutely imperative to use lumps. 2 - Can java moss be used? 3. will there any benefit from using fertilizers and Sphagnum moss? this is an inquiry for a self sustained largish terrarium

I have a question about the active carbon. I found some on a Dutch webshop, but they have two types. They are both meant for brewing wine. They say one is for removing colour and the other is for removing taste and smell, however both are pure activated carbon. Do you know which of these two I should get? Or are they both the wrong type of activated carbon?

Thank you!

hiya, Go with the one to remove taste and smell. My partner says the difference is related to how they produce the "active" part of the carbon and the different sized "pores" that make carbon activated and how they remove the impurities in the alcohol :)

I do love these little wonderlands! I found a rather large bottle at a jumble sale. it is quite heavy. planning a wee garden is what I would like to do. With some collected moss, would it also work to plant a succulent nib? perhaps a mini jade? thank you for sharing yoyr lovely ideas. if you have any other ideas, I coukd try, I would aporeciate it very much!

hiya You have to make sure that whatever mix of plants you use their conditions are compatible. From the succulents I'm familiar with they want a lot less water/moisture in the air than moss but you could alter how you make it such as not sealing it and spray the moss daily, this means the succulent wouldn't be too wet and I think succulents like open air (not sure on this, I'm not too familiar with them). Ferns work well with the moss in closed terrariums.
Good luck!

How small can these get? I'm looking for some projects to do with old light bulbs, would that be an option for me?

Also, what kinds of plants are good for these?

I've done miniature ones in the bottles that essences or food colour comes in. I used the same method but you have to be very aware of how much you are putting in (remember 1/3 filled, 2/3 air). The best plants are those that like a humid environment and are happy without direct sun. Small ferns are great, begonia's and similar.

I will soon be starting a school project in which we have to make a closed jar terrarium in a mason jar for a small snail to survive in for about two months, without ever opening the jar or making holes for air. We have a budget of $6. I'm pretty sensitive and I'm worried about the snail dying in our captivity, so I'm doing everything I can to make sure that my group conducts the experiment in the right way and that the snail survives. I would be thrilled if anybody could offer any advice or tips to make sure I do this right. Thank you!