Building a terrarium in a jar is one of the simplest ways to bring a touch of nature indoors. With just a clear glass jar, a few layers of basic materials, and some carefully chosen plants, you can create a miniature ecosystem that thrives with very little maintenance. A closed jar terrarium works because the sealed environment recycles water and humidity, making it almost self-sustaining.
What makes this project appealing is how accessible it is. Whether it’s a mason jar, a jam jar, or even a pickle jar, almost any clear glass container can be transformed into a thriving display. Closed terrariums suit tropical mosses and small plants, while open jars can house succulents that prefer drier conditions.
The best part is that you don’t need advanced skills or expensive tools to get started. A few pebbles, some soil, moss, and the right plants are all it takes to create a living piece of décor that fits on a windowsill or desk. Once assembled, your jar terrarium becomes a low-maintenance way to enjoy greenery every day.
In short: Making a terrarium in a jar is easy. Layer pebbles, charcoal, soil & plants in a clear jar, then seal or leave open depending on humidity needs.
A jar terrarium is a miniature self-contained garden built inside a clear glass container. It recreates the natural water cycle on a small scale; moisture from the soil and plants evaporates, condenses on the glass, and returns to the roots. This closed loop keeps the ecosystem thriving with very little care. Making one is an easy, sustainable way to bring a touch of greenery indoors, turning an ordinary jar into a living piece of décor.
Closed jar terrarium (sealed lid)
Open jar terrarium (no lid or wide opening)
As a general rule: choose a closed jar for tropical plants and moss; the sealed environment does the work for you. Choose an open jar for succulents and air plants; the airflow keeps them healthy.
We only need a few simple materials to build a jar terrarium. Each plays a specific role in creating a balanced environment that supports plant growth, prevents rot, and keeps the system looking neat and healthy.
The container sets the stage for everything else. A closed glass jar with a tight-fitting lid creates the environment needed for a self-sustaining DIY terrarium. This lid allows water to recycle through evaporation and condensation, which keeps the plants hydrated without frequent watering.
We can use many types of jars:
The most important feature is clarity. Clear glass lets in enough indirect light while making it easy to observe changes inside. Avoid tinted or frosted jars, as they block light and limit visibility.
Size also matters. A small jam jar works for moss-only terrariums, while larger jars provide room for layered soil, pebbles, and several small plants. Always choose a jar that matches the scale of the plants we plan to use.
The first layer inside the jar should be small stones or gravel. This drainage layer prevents water from pooling around plant roots, which will keep your terrarium free from rot. Without it, excess moisture can quickly kill plants in a closed container.
Good options include:
We usually aim for about one-quarter of the jar’s total height to be filled with this material. For example, in a 12 cm tall jar, we’d add roughly 3 cm of gravel.
Before adding, it’s best to rinse the stones to remove dust or dirt. Clean gravel keeps water clearer and prevents unwanted bacteria from developing in the base.
The next layer, adding activated charcoal, is optional, but it makes a big difference in closed terrariums. It absorbs toxins, reduces odours, and helps prevent mould or bacterial growth. This keeps the environment stable over time.
We can buy aquarium charcoal from pet shops or garden centres. Another option is to make our own by burning untreated wood and collecting the charcoal. If we go the DIY route, we must ensure it’s completely free of additives, oils, or chemicals. Standard barbecue briquettes usually contain additives and should be avoided.
To use it, sprinkle a thin layer (about 0.5–1 cm) over the gravel before adding soil. Wetting the charcoal slightly before placing it in the jar helps reduce dust and prevents it from sticking to the glass.
If charcoal isn’t available, moss can sometimes serve as an alternative. While not as effective at filtering, moss does help regulate moisture and adds a natural look to the base layers.
The next thicker layer is the growing medium. A nutrient-rich potting soil or potting mix works best for most terrarium plants. The soil should be slightly moist but not soggy when added.
A good rule of thumb is a 3:1 ratio of soil to gravel. So, if we add 3 cm of gravel, we should follow with about 9 cm of soil. This depth gives roots enough space to spread while keeping the terrarium balanced.
Different blends work well depending on plant choice:
It’s important to avoid garden soil that may contain pests or weed seeds. Using sterilised or a layer of potting soil ensures a clean start for our plants.
Moss is both decorative and functional. It helps cover exposed soil, which prevents erosion when watering and is an easy and fun way to keep it looking natural. Moss also retains humidity, making it useful for maintaining moisture levels in a closed jar.
Common types we can use include:
If we collect moss from outside, it should be rinsed and checked for insects before adding it to the jar. Many garden centres also sell preserved or live moss that’s ready to use.
When arranging moss, we can tuck it between plants, spread it across bare soil, or place it around decorative stones. Over time, it will help care for your terrarium microclimate by holding onto water and slowly releasing it back into the air.
Choosing the right plants is key to keeping your terrarium healthy and balanced. In closed jars, humidity stays high, perfect for tropical and moisture-loving species. Open jars, on the other hand, suit plants that prefer drier air, like succulents or air plants. The table below lists some of the best options depending on the type of terrarium and light conditions.
| Plant Name | Type | Light Preference |
|---|---|---|
| Fittonia (Nerve Plant) | Tropical foliage plant | Bright, indirect light |
| Peperomia (Mini Varieties) | Compact, humidity-loving | Medium to bright, indirect light |
| Pilea depressa | Creeping ground cover | Bright, indirect light |
| Ferns (Mini or Button Fern) | Moisture-loving | Low to medium light |
| Moss (Cushion or Sheet Moss) | Ground cover / moisture stabiliser | Low to bright, indirect light |
| Succulents (for open jars) | Drought-tolerant | Bright, direct light |
| Air Plants (Tillandsia) | Epiphytic, soil-free | Bright, indirect light with airflow |
Tip: For a closed jar, stick to tropical plants and moss that love humidity. For an open jar, choose species that can handle airflow and occasional drying between waterings.
We build a stable base, add protective layers, and then introduce soil, plants, and moss to create a balanced environment. Each step ensures proper drainage, healthy plant growth, and a neat finish that looks natural inside the jar.
We start by rinsing our pebbles or gravel thoroughly to remove dust that could cloud the glass. A clean base helps the water to drain properly and prevents stagnant water from building up.
Spread the pebbles evenly at the bottom of the jar, aiming for about 1–2 cm in depth, depending on jar size. For a more natural look, we slope the layer slightly or create small undulations. This mimics real terrain and adds visual depth when viewed from the side of the jar.
If we want inspiration, many video tutorials demonstrate this step visually, which can be helpful for beginners. Using pebbles of mixed sizes also enhances texture and avoids a flat, uniform appearance.
On top of the pebbles, we add a thin layer of activated charcoal or preserved moss. This step helps filter water, control odours, and reduce the risk of mould growth inside the closed environment.
When using charcoal, we lightly wet it before adding. This reduces dust, prevents smudges on the glass, and makes it easier to settle into place. A layer of about 0.5–1 cm is usually enough.
If we prefer to add a layer of moss, we use a thin pad of dried sphagnum moss. It works as a natural filter, holding moisture and stopping soil from slipping into the drainage layer. Both options serve the same purpose, so it comes down to availability and preference.
A mesh barrier is optional but useful. It sits between the drainage layer and the soil, stopping fine soil particles from sinking into the pebbles over time. This keeps the layers distinct and makes the terrarium look tidy.
We can use fine mesh, a piece of window screen, or any non-biodegradable porous material. It should be cut to fit snugly inside the jar without folding or gaps.
This step is especially helpful in taller jars, where soil can easily migrate downward. In smaller jars, it’s less critical, but it still adds long-term structure and makes maintenance easier.
Next, we add the soil layer. The soil should be damp but not soggy, so we moisten it slightly before adding. This prevents dry pockets and helps plants establish quickly.
We spread the soil evenly over the mesh or charcoal, usually 3–5 cm deep, depending on plant root size. Sloping the soil creates depth and allows us to give larger plants more root space while keeping smaller areas shallow for moss or accents.
Different plant varieties need different blends:
We begin with the largest or feature plant, placing it slightly off-centre for a natural look. This plant sets the focal point. Then we plant small ferns around it to add a decorative feature.
When handling roots, we gently tease them apart and tuck them into the soil without compacting too firmly. Good contact with the soil is enough to help them settle.
Hardscape elements like small rocks, driftwood, or decorative pieces can be added now. They provide contrast and structure. In jars, small, slow-growing, humidity-tolerant plants thrive best, such as Peperomia, Pilea, or mini ferns.
A simple case study: pairing a baby Calathea with cushion moss and a few Peperomia prostrata cuttings creates a balanced mini-ecosystem.
Finally, we place moss around the plants to cover exposed soil and fill gaps. This not only improves the look but also helps retain moisture and stabilises the environment.
We press the moss gently onto the soil, trimming fibrous bases if needed. For a neat finish, we angle moss down towards the glass edge to hide any rough edges.
To keep moss healthy, we mist it lightly and avoid direct sunlight, which can dry it out. Creative touches include arranging moss in small “islands” or creating patterns around stones. This step ties the whole terrarium together and gives it a lush, finished appearance.
A jar terrarium needs only minimal care once it’s established, but a little attention helps it stay vibrant and healthy. By keeping an eye on light, moisture, and cleanliness, you’ll maintain a balanced mini-ecosystem that can thrive for years.
Most terrarium plants prefer bright, indirect light. Place your jar near a window that receives filtered sunlight, but avoid direct rays, they can quickly overheat the glass and scorch delicate leaves. If you notice too much condensation or pale growth, try moving the terrarium slightly farther from the light source. Closed jars do best in warm rooms with stable temperatures, while open jars can tolerate more airflow and drier air.
Because terrariums recycle their own moisture, less is more when it comes to watering. The soil should stay slightly damp, never soggy. A light misting every few weeks into a couple of months is usually enough for closed jars; open terrariums may need more frequent checks. Watch the glass; a fine layer of condensation means humidity is balanced, while constant fog indicates too much moisture. If the jar looks dry for several days, give it a gentle spray to refresh the environment.
Keep the glass clean so you can enjoy the view inside. Wipe the inner surface gently with a soft cloth or paper towel if algae or mineral deposits appear. Remove any yellowing or dead leaves to prevent mould, and trim overgrown plants to maintain shape and airflow. Checking the soil occasionally ensures roots aren’t waterlogged, especially after watering.
Mould: If you see white fuzz or decay, open the jar for a few hours to air it out and remove affected material. Activated charcoal in the base layer also helps prevent regrowth.
Foggy Glass: Persistent fog means excess humidity; leave the lid off temporarily or reduce watering.
Wilting Plants: Too little light or airflow can cause drooping. Move the terrarium to a brighter spot and check soil moisture before watering again.
Start with the drainage layer. Every jar terrarium problem, waterlogging, root rot, and mould, can be traced back to an inadequate drainage base. A 2–3 cm layer of gravel, topped with a thin layer of activated charcoal, gives excess moisture somewhere to go in a container without holes. Without it, even the right plants in the right soil will eventually fail.
In our experience at Miyagi Bonsai, the most common jar terrarium mistake is overwatering at setup. The sealed system recycles moisture internally; adding too much water before sealing creates anaerobic conditions that cause mould and root rot within weeks. Add less than you think you need, seal the jar, and observe the condensation pattern over the first few days before deciding whether more water is required.
Miyagi Bonsai stocks a carefully chosen range of jar terrarium supplies, including pre-selected plant combinations, substrate kits, activated charcoal, sphagnum moss, and complete beginner terrarium kits, with next working day UK delivery available on most orders. The products and recommendations in this guide reflect what we stock, use and see working for our customers every day. We are rated 5 stars across over 100 Google reviews, and our team is on hand by email and phone if you have any questions about jar terrarium setup, plant selection, or long-term care.
Explore Miyagi Bonsai’s beginner terrarium kits and tropical moss selections to start your own living display.
Before you start creating your own jar terrarium, it helps to understand a few common questions people ask. These quick answers cover plant choice, watering, care, and common mistakes so your mini ecosystem thrives from day one.
For a closed jar, choose tropical plants that thrive in high humidity and low to medium indirect light: fittonia, compact ferns, Pilea depressa, and cushion moss are the most reliable and widely available choices. Avoid succulents, cacti, and air plants in closed jars as they will rot in humid conditions.
For an open jar, succulents (Echeveria, Haworthia) and air plants (Tillandsia) are the best options; they need good airflow and prefer to dry out between waterings. The most important rule is to match all plants in the same jar to the same humidity and light requirements; mixing moisture-loving and drought-tolerant species in one container will result in one group declining rapidly.
A closed jar terrarium rarely needs additional watering once established; the sealed water cycle recycles moisture internally, and the system can go weeks or months without intervention. The clearest indicator is condensation: a light misting on the glass in the morning that clears by afternoon is healthy. If the glass stays bone dry for several days, add a small amount of water using a spray bottle.
If heavy condensation persists throughout the day, briefly remove the lid to allow excess moisture to escape. Open jar terrariums need more frequent monitoring; check soil moisture every one to two weeks and water when the top layer feels completely dry.
A minimum volume of 1–2 litres is recommended for a first jar terrarium. Larger jars, 3 litres or more, create a more stable microclimate, give plant roots more space to develop, and are more forgiving of minor watering and placement errors. Small jars under 500 ml can work for moss-only setups, but are less stable and require more careful monitoring.
Wide-mouthed jars are easier to plant and maintain than narrow-necked bottles, which require long tweezers or chopsticks for planting. As a starting point, a standard 1-litre mason jar or a wide-mouth apothecary jar of similar volume offers the best balance of accessibility and stability for beginners.
Yes, activated charcoal is beneficial but not essential. Its primary role is to filter impurities, absorb odours, and reduce mould growth in the substrate. If charcoal is unavailable, a thin layer of sphagnum moss between the drainage gravel and the soil performs a similar function by filtering water movement and adding mild antifungal properties.
The terrarium will work without either, but the risk of mould and substrate contamination is slightly higher over time. If charcoal is not available at setup, it can be added at a later repot. Always use horticultural or aquarium-grade activated charcoal, barbecue charcoal contains additives that are harmful to plants.
The most reliable indicator for a closed jar is the condensation pattern on the glass. A light, misty condensation visible in the morning that clears during the day is the sign of a well-balanced system; no watering is needed. If the glass has been completely clear and the soil appears dry for several consecutive days, add a small amount of water with a spray bottle.
For an open jar terrarium, press a finger 1–2 cm into the soil; if it feels dry at that depth, water lightly. If it still feels damp, wait another few days and check again. Never water on a fixed schedule; always check moisture levels first.
A closed jar terrarium has a sealed or tight-fitting lid that traps moisture, creating an internal water cycle. Moisture evaporates from the soil and plants, condenses on the glass, and drips back down; the system recycles its own water and requires minimal watering. Closed jars are suited to tropical plants and mosses that thrive in high humidity.
An open jar terrarium has no lid or a wide, unsealed opening that allows moisture to escape and air to circulate. Open jars suit succulents, cacti, and air plants that need lower humidity and good airflow, but require more frequent watering as moisture evaporates. The choice between the two should be driven entirely by the plants you want to grow.
Yes, almost any clear glass container with a tight-fitting lid can be used for a closed jar terrarium. Mason jars, jam jars, pickle jars, apothecary jars, and even large drink bottles all work well. The key requirements are that the glass is clear (not tinted or frosted), the container is large enough to accommodate a drainage layer, soil depth, and at least one small plant, and, for closed terrariums, the lid fits securely enough to maintain humidity.
Rinse and sterilise any repurposed food jars thoroughly before use to remove any residue. Avoid containers with coloured or opaque glass, as they reduce the light reaching the plants and make it impossible to monitor moisture and root development.
The most common mistake is overwatering at setup; adding too much moisture before sealing creates anaerobic conditions that cause mould and root rot within weeks. Add less water than you think you need, seal the jar, and observe the condensation pattern before adding more.
The second most common mistake is mixing plants with incompatible care needs; placing succulents alongside mosses or ferns in the same closed jar will result in one group declining as its moisture needs conflict with the other.
The third is using garden soil rather than a sterile potting mix; garden soil carries pests, weed seeds, and pathogens that thrive in the humid conditions of a jar terrarium. Always use a purpose-built substrate or a clean potting mix.
A well-built closed jar terrarium can last anywhere from several months to several years, and in exceptional cases, indefinitely. The main factors are initial plant compatibility, substrate quality, and the absence of overwatering at setup. A correctly balanced closed jar with compatible tropical species and a good drainage layer will largely manage itself and can remain stable for two to five years before individual plants need replacing or the substrate needs refreshing.
Open jar terrariums typically require more active maintenance and have a shorter natural lifespan as moisture evaporates and substrate compacts over time. The most reliable way to extend the lifespan of any jar terrarium is to introduce a springtail culture; a small Folsomia candida colony will manage mould and organic waste naturally and indefinitely.
For a closed jar, the three most important habits are: checking condensation rather than watering on a schedule, removing any dead or yellowing leaves promptly to prevent mould, and ensuring the jar receives bright indirect light rather than direct sun.
For an open jar, allow the soil to dry fully between waterings, trim any overgrowth to maintain airflow, and check for pests at each watering session. For both types, the most effective long-term maintenance addition is a springtail culture; introduced once the terrarium is established, springtails manage mould and organic decomposition continuously without any further intervention.
