Terrariums are a great way to display your special succulents and houseplants. They look like a little garden display.
There are many ways to build a terrarium, but before you start putting it together, you should read about how to build a proper base with layers of soil to keep your terrarium, and plants healthy.
There for, the substrate that you use to build your terrarium can make or break it.
Building a terrarium is like building a house.
For your plants to thrive in the terrarium, they will need:
- a solid base
- proper drainage
- perfect environment
Plants are basically soil that needs to be held in place and given basic gas exchange (oxygen) for its roots, and be allowed to take up water and nutrients.
Our Main Goal: By intentionally creating the environment, we can build a terrarium that looks good and helps to provide a great habitat for plants to grow successfully.
How to Layer Terrarium Substrate?
Drainage Layer
The drainage layer is important to make sure there is excess water held at the bottom of your terrarium without drowning the roots or causing root rot.
Usually, its the very bottom layer, but some people add a decorative layer or some charcoal first.
Put a drainage substance 1-2 inches thick at the base of your terrarium (amount will be dependent on the size of your container).
Do not skip on this layer because it provides additional drainage in case of excess water even for the plants, so they are not submerged in water and not developing rotted roots.
For a drainage layer, pea gravel is the most commonly used, but small river pebbles would work as well, colorful aquarium gravel would also work, or you could use interesting little rocks you have found.
Nice touch: decorative stones, marbles, and sea glass are all very good options too.
The Moss Layer
Next, you’ll want to pop a layer of sphagnum moss or dried moss on top of your drainage layer.
This will keep the soil from moving down and will soak up a little extra moisture. This added layer will add more texture and color to the middle layers of your terrarium.
Make sure it is deep enough to hold the soil a little higher to prevent any soil from seeping into the drainage area.
Layer of Charcoal
This piece isn’t required, but essential for the health and life span of your terrarium.
This layer acts as a barrier in your terrarium:
- It’s filtering out pollutants
- It’s keeping the smells of toxins from developing
- It’s functioning well above moss layer
Although it may be added at the base of terrarium by some.
Your terrarium can function effectively without this layer, though you’ll have to be extra diligent to keep the conditions just right.
Soil Layer
The soil layer is basically where your plants are going to grow.
It will anchor the roots and provides the nutrients that plants need to grow.
Think about what type of terrarium you’re making and choose the soil based on the type of plants you are going to put in the terrarium.
If you’re using tropical plants, you want to look for:
- Aeration
- Adequate draining
- Water retention
The thickness of this layer will also be based on the size of your plants.
It should be thick enough to accommodate the biggest root ball, but still allow the plant roots to grow on either side.
Decorative Soil Layer
Using decorative layers is usual as pea gravel style or decorative rocks, putting figurines in the plants, and adding waterfall formations into a project are ways to use decorative layers.
Here is one thing to note: you will want to include materials used for decoration that are non-reactive.
That is why using stones, petrified wood, or crystals will be great choices, as they will NOT deteriorate or rot away over time.
Plant Layer
Deciding on the plants is one of the enjoyable parts of building the terrarium.
When looking to construct a smaller terrarium, it’s better to select smaller plants so that as they grow they won’t crowd each other out.
Since they need different amounts of moisture, you need to go with only one type of plant; cactus, all tropical plants, or all succulent plants.
A little reminder: Succulent terrariums need a dryer environment with an open cover and less moisture, whereas tropical terrariums can have a closed lid with humid, wet conditions.
Open and Closed Terrarium Substrate
When creating your terrarium, one of the first decisions you’ll have to make is whether you want a closed or open terrarium.
Closed Terrarium
It’s a sealed terrarium with a lid, so moisture can build up inside! These are the best choice for tropical plants that need more humidity, as well as a wet – but not saturated! – medium.
Water is going to cycle continuously in a closed terrarium with lots of light. Water will evaporate, condense on the sides of the container and then drip back into the soil.
Because there is nowhere for the water to escape, the container will remain at the same moisture level as it was on the day you closed it.
Open Terrarium
An open terrarium has a healthier environment for succulents and cactus because it allows moisture to escape and evaporate. Succulents, cactus, and even air plants can do well in an open terrarium, but they would die in a closed terrarium.
Open terrariums can also have a much wider variety of substrate characteristics because once again, you can enhance your watering when there is a problem.
It works: if you prefer this style of terrarium which is more manageable, you can add coconut coir or something similar to your substrate to increase water retention and allow you to water less frequently.
Recommended Terrarium Soil/Substrate
Coir
Coconut coir is a great organic, fibrous material made from coconut husks.
It can be found in a lot of different forms such as a single dry brick or in bags of coarse chips or finely crushed stuff.
The chips or fibers provide more drainage but the powders are much easier to plant in.
Coir is incredibly light and fluffy, which means high root air spaces, high moisture retention, and it doesn’t settle under weight like regular soils used in terrariums.
Coir is also valued for its “stability” and durability. It is a “finished” product, so it won’t degrade in your terrarium.
While coir is not molestable, you can control drainage and moisture easier than with random soil types.
Sphagnum Moss
Sphagnum moss is, without a doubt, a true centerpiece of the terrarium and vivarium industry in both live and preserved forms, but for substrates, preserved is preferred.
Like coir, Sphagnum moss below dirt can benefit terrariums for its awesome water retention properties and fluffy mass.
Additionally, Sphagnum moss has unique antibacterial properties which help reduce bacterial growth and therefore slow degradation.
It is sometimes used as a growth medium by itself, and other times as a substrate barrier, and even as an addition to other mixes.
Sphagnum moss is so versatile that it can be used as both a substrate and an additive based on how you are using it!
Aquarium Soil
Aquarium dirt, or dirt from an aquarium, is regular soil that is been baked into dry pellets.
It’s an interesting media because it has all of the nutrients, and positive growth features of regular potting soil but has a lot better drainage.
Because, the pellets are round and do not stack together in uniformity.
They also have a little density of their own, therefore, they will resist compaction over the long haul. Aquarium dirt has recently become popular and it may be the one media that you can have with only its own coverage.
Good To Know: Although it is hard to plant in on its own, it works like a base, not a all-in-one substrate.
Terrarium Soil/Substrate Supplements
Perlite
Perlite is a type of white volcanic glass that looks a lot like polystyrene balls.
It’s lightweight, absorbent, and useful in tropical terrariums.
Its odd shape allows it to hold water on its outside surface but not inside, making it a great source of constant water for your plants without making a wet mix.
The granular shape of the material also helps de-aerate a substrate mix. A little perlite goes a long way!
Vermiculite
In terms of function, vermiculite is pretty much like perlite, although it looks and acts differently.
It’s a mineral, like flaky brown pebbles.
Vermiculite holds water much better than perlite and could be a great addition to substrates to use for tropical plants because they require moisture.
Orchid Bark
This method increases soil grit and introduces aeration in a more organic manner.
It’s a mix of bark shavings that helps create structure and space for a soil medium.
Bad News: The actual problem is finding a small mix for terrariums, it usually is pretty thick.
Earthworm Casting
If you are using pure cocofiber as your soil media, you’re going to need to add minerals to your grow media.
Please limit the compost you add to only using commercial compost. Do not add any homemade compost that may contain rotting materials, no matter how tempting it may be.
Earthworm castings are also a highly effective and readily available option. It is completely natural fertilizer; it is well-draining and also holds a lot of water.
Charcoal
Because of its super porous nature, it can latch onto things like terrarium pollutants making it a widely used “cleaning” material.
Due to its porosity, it is excellent at retaining moisture and is often thought of as keeping and providing nutrients for plant roots.
It comes in a variety of formats but a fine powder is likely the easiest to add into a substrate mix.
Sand
You can just add sand to your growing medium to improve aeration and drainage.
Horticultural sand is the best sand, but any sand will work. If you are looking to create a desert terrarium, you are going to be using a lot more sand.
The same is true for any type of cactus or succulent combo. If you can find black sand, that is better.
This way, the substrate will be less visible, and the darker substrate provides better contrast with green plants.
Watering and Lighting in A Terrarium
The tropical terrarium hates direct sunlight.
In your home, it is best to put the terrarium in a bright room with only indirect sunlight in the morning. A tropical terrarium should be watered about once or twice per week so that the soil is damp but not flooded.
It too likes to be misted with a spray bottle of water about once per week. Think rainforest.
The succulent terrarium can take a little direct sunshine in the early morning followed by nice, solid afternoon indirect sunlight.
But keep in mind, the succulent terrarium will enjoy sitting outside, in indirect sunlight for a few hours, about once per week (not in the cold). The succulent terrarium likes a little drink, but not a flood, because it is not a cactus.
During the warm months, spray each succulent once a week to every two weeks using a spray bottle.
During the winter months, you can probably just spray gently every 10 days or so.
Follow your intuition: when your terrarium is thirsty, it will dry out and your plants will tell you!
Final Thoughts
Terrariums aren’t places for plants to grow unless the drainage and soil layers are carefully controlled.
In the decorative layer, this is where you could add some personalization to your terrarium. This layer could be more moss or something funky, like colorful gravel for aquariums.
You could also put layers of decorative sand if you want. These materials will provide protection for the roots of the plants and ossibly keep the roots anchored into the soil and keep moisture where it is the most important.
You can create a decorative look to your layers by making sure your layers are thick enough to be able to see differences in layers.
You can also shape the layers to create a flow inside them, for example, raise one side and lower the other.
You could come up with some great looks by using different colors of gravel or sand in layers and you could even match the color of the gravel and sand to the color of the flower blooming inside.