Below, you’ll find a step-by-step guide to help you care for your closed terrarium properly.
1. Monitor Moisture Levels Carefully
One of the most important aspects of caring for a closed terrarium is managing humidity. Because the lid traps moisture, water continuously cycles inside the container. If you see excessive condensation on the walls—especially if it drips—it means there is too much moisture. In this case, simply remove the lid for a few hours to allow some of the water to evaporate.
On the other hand, if you notice that the soil looks dry and there is little or no condensation, lightly mist the plants and soil with distilled or filtered water. Be conservative—overwatering is one of the most common mistakes with lidded terrariums. Aim to keep the soil slightly damp, not soggy.
2. Provide the Right Amount of Light
Light plays a crucial role in keeping your terrarium thriving. Closed terrariums do best in bright, indirect light. Placing your terrarium near a north- or east-facing window works well. Avoid direct sunlight, as the glass can act like a magnifying lens and quickly overheat the plants, leading to scorched leaves and excess condensation.
If natural light is limited, consider using fluorescent or LED grow lights. Make sure the lights are not too close to the terrarium, and give your plants about 10–12 hours of light per day.
3. Choose the Appropriate Plants
The types of plants you grow will directly impact how easy your terrarium is to care for. Because a closed terrarium retains moisture, tropical plants that prefer humid conditions are ideal. Popular options include:
- Ferns
- Fittonia (nerve plant)
- Peperomia
- Mosses
- Pilea
Avoid succulents and cacti in closed terrariums—they prefer dry, arid conditions and will almost certainly rot in high humidity.
4. Maintain Air Circulation Occasionally
Even though a closed terrarium is designed to stay sealed most of the time, it still benefits from occasional fresh air. About once every week or two, remove the lid for 30–60 minutes. This helps prevent mold growth and allows excess moisture to escape. If you notice any mildew forming on plant leaves or glass, leave the lid off longer and wipe the affected area with a clean, damp cloth.
5. Watch for Mold and Decay
Mold is one of the most common challenges in closed terrariums. Check regularly for white, fuzzy mold on plant stems, leaves, or the soil surface. If you spot any, remove affected parts promptly. You can also sprinkle a small amount of activated charcoal on the soil to help reduce bacteria and odor. Keeping the terrarium clean and avoiding overwatering are your best defenses against mold.
6. Prune and Clean as Needed
Closed terrariums can become overgrown quickly because plants often thrive in the humid environment. Trim back any leaves or stems that touch the glass to improve airflow and prevent decay. Remove any fallen leaves or debris as soon as you see them to reduce the risk of fungal growth.
Wipe the inside of the glass periodically to keep it clear of condensation stains or algae. Use a soft cloth or paper towel for this, and avoid harsh chemicals.
7. Fertilize Sparingly
Because closed terrariums are low-nutrient environments, you don’t need to fertilize often. In fact, too much fertilizer can cause plants to grow too quickly and outgrow the space. If you do choose to feed your plants, use a highly diluted liquid houseplant fertilizer (about 1/4 strength) no more than twice per year.
8. Keep the Temperature Consistent
Most closed terrariums thrive in average household temperatures between 60–75°F (15–24°C). Avoid placing your terrarium near heat vents, radiators, or drafty windows, as sudden temperature fluctuations can stress the plants and upset the moisture balance.
Conclusion
A closed terrarium with a lid is a beautiful, low-maintenance way to enjoy a slice of nature indoors. The key to success is balance: the right amount of moisture, indirect light, occasional fresh air, and regular monitoring. By following these care tips, you’ll create a stable miniature ecosystem that stays healthy and vibrant for months—or even years—to come.
Remember, each terrarium is unique. Pay attention to how yours responds to its environment, and adjust your care routine as needed. With a little attention and observation, your closed terrarium will reward you with lush, thriving greenery in any room of your home.