What size glass container for a terrarium depends on several key factors that many plant enthusiasts overlook when starting their miniature ecosystem journey. The container you choose becomes the foundation of your entire terrarium project, influencing everything from plant health to maintenance requirements.
People often ask this question because they want their terrarium to thrive rather than merely survive. Having built hundreds of terrariums over the years, I’ve seen how the wrong container size can turn an exciting project into a frustrating experience, while the right choice creates a flourishing miniature world that brings joy for years.
What size glass container for a terrarium?
The ideal terrarium container size depends on your plant selection: use 1 to 3 plants for a small container (less than 6 inches in diameter), and 4-5 for a large container (over 6 inches in diameter). However, successful terrarium building goes far beyond these basic guidelines.
Small containers: Desktop delights (4-8 inches diameter)
Small containers work beautifully for beginners and limited spaces. Small terrarium plants range from 1-6 inches in height, making them perfect companions for compact containers. Mason jars, small apothecary jars, and geometric terrariums fall into this category.
The charm of small containers lies in their manageability. You can easily move them around your home, experiment with different locations, and make adjustments without major disruption. They’re also budget-friendly, allowing you to practice terrarium techniques without significant investment.
However, small containers present unique challenges. Limited soil volume means faster moisture fluctuations, requiring more careful monitoring. Plant selection becomes crucial—choose slow-growing species like small ferns, moss, or baby’s tears that won’t quickly outgrow their space.
Medium containers: The sweet spot (8-12 inches diameter)
Medium-sized containers offer the best balance for most terrarium enthusiasts. Medium plants range from 6-12 inches in height, giving you more creative flexibility while maintaining manageable proportions.
This size category accommodates most popular terrarium plants comfortably. You can create interesting compositions with different plant heights and textures without overcrowding. The increased soil volume provides better moisture buffering, making these containers more forgiving for beginners.
Fish bowls, larger apothecary jars, and small aquarium tanks work perfectly in this range. The wider opening typical of medium containers makes planting and maintenance significantly easier than working with small vessels.
Large containers: Ecosystem enthusiasts (12+ inches diameter)
Bigger terrariums will be healthier than small ones due to more volume providing a buffer for changes in soil and air chemistry. Large containers allow for complex ecosystems with multiple plant species, varied heights, and elaborate decorative elements.
Consider repurposed fish tanks, large glass bowls, or custom-built cases for this category. Large terrariums have more space, more options, and ultimately more plants, but they also require more initial investment and ongoing commitment.
The advantages include stable microclimates, room for plant growth, and stunning visual impact. You can incorporate taller plants, create distinct zones within your terrarium, and develop truly impressive displays.
Height considerations: Room to breathe
Container height matters as much as diameter. You will want to aim for about 2-3 extra inches of space in addition to the predicted height of your tallest plant. This extra space accommodates essential drainage layers and allows for natural plant growth.
Closed terrariums especially need adequate height for air circulation and humidity regulation. Insufficient height leads to condensation problems and potential plant rot from excessive moisture contact.
Opening width: Access matters
If you’re just getting started with terrariums, I’d recommend going for a container with a nice wide opening to give you lots of space to maneuver. This practical consideration often gets overlooked in favor of aesthetics.
Narrow openings make planting difficult, maintenance challenging, and plant removal nearly impossible when needed. Your hands should fit comfortably through the opening with room to manipulate small tools.
Material and quality considerations
Glass containers provide a clear view and maintain the moisture levels necessary for a thriving terrarium. Choose clear glass over colored varieties, as colored glass filters necessary light for plant growth.
Give preference to containers with thinner glass as it allows more light through but also allows more heat out, reducing the greenhouse effect a little bit. This helps prevent the “cooking” effect that can harm your plants.
For closed terrariums, ensure your container can seal properly. Test the container for leaks by filling it with water before use. A leaking container indicates it’s not airtight, making it unsuitable for a closed terrarium.
Matching container to terrarium type
Open terrariums offer more flexibility in container choice since humidity control isn’t critical. Almost any attractive glass vessel works, from vintage bowls to modern geometric shapes.
Closed terrariums require containers that can seal effectively. Look for pieces with tight-fitting lids, or be prepared to create custom covers using cork, acrylic discs, or glass plates.
Conclusion
Container size selection forms the foundation of terrarium success, influencing everything from plant health to maintenance requirements. Start with medium-sized containers if you’re uncertain—they offer the best balance of manageable size and ecosystem stability. Remember that thoughtful container selection at the beginning saves countless headaches later.
Just last month, I helped a friend transition her struggling small-jar terrarium into a beautiful 10-inch glass bowl. The plants that had been cramped and struggling suddenly flourished with adequate space and better moisture regulation. Her excitement reminded me why choosing the right container size matters so much—it transforms terrarium keeping from a chore into pure joy. That transformation perfectly captures why I’m passionate about sharing these techniques that turn anyone into a confident ecosystem architect.