Creating your first terrarium can feel overwhelming, but it doesn't have to be. This comprehensive guide walks you through everything you need to know to build a thriving miniature ecosystem, from understanding the basics to selecting your first plants and container.
What Exactly Is a Terrarium?
A terrarium is essentially a miniature garden enclosed in a glass container. The concept originated in the 1840s when English botanist Nathaniel Bagshaw Ward accidentally discovered that plants could thrive in sealed glass cases. This discovery revolutionised plant transportation and sparked a Victorian-era obsession with these elegant glass gardens.
Modern terrariums come in two primary types: open and closed. Open terrariums have an opening that allows air circulation and are ideal for plants that prefer drier conditions, such as succulents and cacti. Closed terrariums are sealed environments that create their own water cycle, making them perfect for humidity-loving plants like ferns and moss.
Key Takeaway
Terrariums are self-contained ecosystems that require minimal maintenance once properly established. The key to success is matching your plant choices with the right type of container.
Essential Components of Every Terrarium
Regardless of whether you choose an open or closed design, every successful terrarium contains several essential layers that work together to create a healthy environment for your plants.
The Drainage Layer
The bottom layer of your terrarium should consist of small pebbles, gravel, or expanded clay balls (LECA). This layer typically measures between 2-5 centimetres deep, depending on the size of your container. Since terrariums lack drainage holes, this layer prevents water from pooling around plant roots, which can lead to root rot—the most common cause of terrarium failure.
The Separation Layer
Above the drainage layer, add a thin layer of activated charcoal mixed with sphagnum moss or a piece of mesh fabric. The charcoal serves a crucial purpose: it absorbs toxins and prevents bacterial growth, keeping your terrarium fresh and odour-free. The moss or mesh prevents soil from filtering down into the drainage layer.
The Growing Medium
The soil layer is where your plants will establish their roots. For most terrarium plants, use a well-draining potting mix. Avoid garden soil, which is too dense and may contain pests or diseases. For succulents and cacti, use a specialised cactus mix or add extra perlite to improve drainage.
Choosing Your Container
The container you select will influence which plants you can grow and how much maintenance your terrarium requires. Glass containers are preferred because they allow light to penetrate while providing clear visibility of your miniature landscape.
For beginners, we recommend starting with a medium-sized container—something around 15-25 centimetres in diameter. This size is large enough to create an interesting arrangement but small enough to manage easily. Avoid containers that are too small, as they leave little room for error and can overheat quickly.
Container Selection Tips
- Choose clear glass for maximum light transmission
- Ensure the opening is wide enough for your hands or tools
- Consider how the container will look in your intended location
- For closed terrariums, verify the lid creates a good seal
Selecting Plants for Your First Terrarium
Plant selection is perhaps the most critical decision you'll make. The golden rule is to choose plants with similar light, water, and humidity requirements. Mixing drought-tolerant succulents with moisture-loving ferns is a recipe for disaster—one group will inevitably suffer.
Best Plants for Closed Terrariums
Closed terrariums maintain high humidity levels, making them ideal for tropical plants. Excellent choices for beginners include fittonia (nerve plant), which comes in stunning pink and white varieties; miniature ferns like maidenhair or button fern; and various moss species that create a lush carpet effect. Peperomia varieties also thrive in these conditions and add interesting leaf textures.
Best Plants for Open Terrariums
Open terrariums suit plants that prefer drier conditions. Succulents are the obvious choice—echeveria, haworthia, and sedums are particularly forgiving for beginners. Air plants (Tillandsia) work wonderfully in open containers and require only occasional misting. Small cacti can also work, though they require even less water than succulents.
Building Your First Terrarium: Step by Step
Now that you understand the components and have selected your container and plants, it's time to build your terrarium. Set aside about an hour for this process—rushing leads to mistakes.
Start by thoroughly cleaning your container with warm water and letting it dry completely. Any residue or moisture can encourage mould growth. Next, add your drainage layer, spreading the pebbles evenly across the bottom. Follow with the charcoal layer, then the soil.
Before planting, arrange your plants while they're still in their nursery pots. This lets you visualise the final design without committing. Consider height variation, colour contrast, and how the plants will grow over time. Once satisfied with your arrangement, remove each plant from its pot, gently loosen the roots, and plant it in the soil.
After planting, add decorative elements if desired—small stones, driftwood, or miniature figurines can add personality. Finally, water sparingly. For closed terrariums, mist lightly; for open terrariums with succulents, wait a few days before watering to let any damaged roots heal.
Pro Tip
Less is more with watering. It's far easier to add water than to remove it. Start with less than you think you need, observe your terrarium for a few days, and adjust accordingly.
Placement and Light Requirements
Proper placement is essential for terrarium health. Most terrarium plants thrive in bright, indirect light—think near a window but not in direct sunlight. Direct sun can overheat a closed terrarium within minutes, essentially cooking your plants. Even open terrariums with succulents should avoid harsh afternoon sun in Australian summers.
If you lack natural light, artificial lighting can work well. LED grow lights are energy-efficient and provide the spectrum plants need. Position the light 15-30 centimetres above your terrarium and run it for 10-12 hours daily.
Common Beginner Mistakes to Avoid
Understanding common mistakes helps you avoid them. Overwatering is the number one killer of terrariums—the enclosed environment means water has nowhere to go. Signs of overwatering include foggy glass that doesn't clear, yellow leaves, and a musty smell.
Another common error is using the wrong soil. Regular potting mix retains too much moisture for succulents, while cactus mix is too dry for tropical plants. Match your soil to your plants' needs.
Finally, many beginners place their terrariums in unsuitable locations—too dark, too sunny, or near heating vents. Observe your terrarium's location at different times of day before committing to a spot.
Ongoing Care and Maintenance
Once established, terrariums require minimal maintenance. Closed terrariums may need opening occasionally to release excess moisture or add a small amount of water if the soil appears dry. Open terrariums require regular watering based on the plants' needs—typically every 1-2 weeks for succulents.
Prune plants that grow too large for their space. Remove any dead or dying leaves promptly to prevent mould. Clean the glass inside and out periodically to maintain clear visibility and maximum light transmission.
Your Terrarium Journey Begins
Creating a terrarium is both an art and a science. Don't be discouraged if your first attempt isn't perfect—every terrarium teaches you something new. Start simple, observe carefully, and adjust based on what you learn. With patience and attention, you'll soon have a thriving miniature ecosystem that brings nature indoors.
Ready to explore more? Check out our complete plant selection guide or learn about choosing between open and closed terrariums.