Terrariums are billed as the ultimate no-maintenance houseplant setup, so it’s not surprising that many newbie terrarium owners are a little miffed when, a few months in, things start going wrong.
Perhaps the glass is misty and filmed with a green goo. Or the once-neat foliage of a fern has grown so much that it is threatening to push up the lid and smother the other plants. Or, worse of all, there’s just a pile of brown, moldy mush where a succulent once stood.
While there are many terrarium websites and books full of terrarium projects to undertake, few address in detail how to troubleshoot problems, or acknowledge that even the most carefully planted terrarium will probably need a revamp once or even twice a year. This partly depends on the size of the container: as botanist James Wong, pointed out recently, a terrarium of at least 30 by 30 centimeters (approximately 12 by 12 inches) is far more likely to create a stable, long-term environment for plants. You can keep plants in smaller glass containers than that: just don’t expect them to look exactly the same in a year.
Terrariums are often touted as being low maintenance and easy to care for. So it can be disheartening when, after a few months, things start to go wrong. Perhaps the glass has become fogged with green algae. Or the once-tidy foliage of a fern has grown unruly, threatening to push up the lid. In some cases, the worst discovery is a pile of brown, rotting mush where a plant used to thrive.
While there are plenty of sources focused on terrarium construction and design, troubleshooting dying terrariums doesn’t get as much attention. The truth is, even the most meticulously planted terrarium will likely need some rehab every 6-12 months. Container size plays a role too. Recently, botanist James Wong pointed out that a terrarium of at least 12 x 12 inches has a much better chance of providing plants a stable, long-term environment. It’s possible to keep plants in smaller containers, just don’t expect them to maintain their original look long-term.
The good news is, with some detective work and TLC, it’s often possible to nurse a failing terrarium back to health. Follow this step-by-step guide to get your plants back on track and restore balance to the mini ecosystem.
Diagnose the Problem
Carefully observe the terrarium to identify any issues. Are plants rotting or discolored? Does the soil look bone dry or muddy? Is there green scum on the glass? Smell anything funky? Pinpointing problems is key before taking action. The most frequent terrarium killers are improper watering, excessive light/heat, and poor air circulation.
Fix Watering Problems
Too much or too little water causes more terrarium deaths than anything, Plants wilting despite wet soil indicates overwatering, Allow more ventilation to lower humidity, Remove soaked moss and replace with dry sphagnum moss to absorb extra moisture,
If plants are shriveling and soil is dusty, give small drinks with a pipette or spray bottle right to the base of plants. Mist moss layers lightly. Increase watering frequency while closely monitoring soil moisture.
Adjust Light and Temperature
Plants turning brown or lanky often results from too much light or heat Move the terrarium away from sunny windows and use sheer curtains to filter light Moderate temps with air conditioning or fans,
If plants seem small and compact they likely need more sunlight. Gradually relocate the terrarium to brighter spaces watching for signs of stress. Rotate it so all sides get even light.
Increase Air Circulation
Stale air and high humidity breed mold, algae and fungal diseases. Prop open the lid with a stick for a few hours daily to improve airflow. Add a small battery-powered fan to gently circulate the air. Just don’t leave the lid open too long or plants may wilt.
Prune Overgrown Plants
It’s easy for terrarium plants to become overgrown. Carefully trim back any plants touching glass or overwhelming their neighbors. Cuttings can be propagated in potting mix for later replanting. Pruning increases air flow and light penetration.
Clean the Glass
Wipe down the interior glass with paper towels and mild cleaners like diluted vinegar. Use a soft cloth to gently remove stubborn algae buildup. Completely rinse and dry the glass before replacing plants. Regular cleaning prevents future scum issues.
Remove Dead Material
Eliminate any rotting plant matter, dead leaves and contaminated soil. Clip away dead roots and scrub plant containers to destroy mold spores. Replace any decaying moss. This removes disease sources and gives plants a fresh start.
Consider Replanting
If many plants have died or the terrarium is beyond saving, a complete replant may be needed. Wash the container in hot soapy water. Use fresh potting mix and rinsed pebbles/gravel for drainage. Choose plants suited to the new lighting and humidity levels. Adjust care routines to prevent future problems.
With attentive troubleshooting and care, even severely neglected terrariums can bounce back. Be patient and allow plants adequate time to recover between adjustments. A revived terrarium may not match the original, but with trial and error it can thrive again. Don’t let problems progress too far before taking action – catching issues early makes salvaging dying terrariums much easier.
Choosing the Right Plants and Materials
Prevention is better than a cure. Picking appropriate plants and materials from the start significantly reduces problems later on.
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Select plants suited for terrarium conditions – consider humidity, light needs, growth rate. Popular choices include ferns, mosses, small tropical plants.
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Use quality terrarium soil mix – well-draining and specifically formulated to prevent overwatering and root rot.
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Include drainage layer – pebbles or gravel at the bottom improve drainage and keep water from pooling around roots.
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Consider activated charcoal – helps filter impurities and reduce odors.
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Maintain cleanliness – regularly remove dead leaves and debris to prevent harmful bacteria/fungus buildup.
Pro Tip: Understand Closed vs. Open Terrariums
The terrarium type – closed or open – greatly impacts care.
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Closed terrariums create a self-sustaining humid ecosystem. Need less frequent watering but more prone to overwatering and fungal problems.
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Open terrariums have better ventilation, suitable for plants preferring drier conditions like succulents. Require more frequent watering.
Troubleshooting Questions
How do I know if my terrarium is overwatered?
Signs include yellowing leaves, mushy stems, standing water, mold growth, foul odors, and constantly soggy soil.
How often should I water the terrarium?
Closed terrariums – Every few months.
Open terrariums – Weekly or when soil is dry.
What kind of water is best?
Use distilled water to prevent mineral buildup in soil over time.
Why is my terrarium getting moldy?
Excessive moisture and poor ventilation cause mold. Improve airflow by opening more or adding ventilation holes.
Can I use regular potting soil in a terrarium?
No. Terrariums need well-draining mixes specifically formulated to prevent root rot.
What are the best terrarium plants?
Closed terrariums – Ferns, mosses, small tropical plants.
Open terrariums – Succulents, cacti.
How much light does a terrarium need?
Indirect or filtered light. Avoid direct sun which can scorch leaves.
Reviving a Dying Terrarium Takes Patience and Persistence
Bringing a dying terrarium back to life requires careful observation, diagnosis, and action. Understanding your plants’ needs and providing the proper conditions transforms a struggling ecosystem into a thriving world in miniature. Remember to be patient and persistent, and don’t be afraid to experiment until you find the perfect balance. Pay close attention to avoid problems progressing too far. Your attention and care can make the difference between terrarium life and death.
The Glass is Dirty
If your glass is green, it’s a sign that algae has started setting up home. If you have a large tank-style aquarium with flat sides, you can use an aquarium scraper or even an old credit card to remove algae easily. On curved glass, paper towels or a clean rag are perfect. White streaks are usually caused by mineral deposits caused by watering with tap water; if you can, use rainwater or distilled water to fix the problem. You may be able to wipe away the streaks with a cloth dampened with lemon juice or vinegar (keep this well away from your plants). Then follow up with a cloth dipped in rainwater or distilled water. If that doesn’t work, you’ll need to take apart the terrarium, clean the glass thoroughly with vinegar, rinse, and reassemble.
The Plants Are Leaning to One Side
Your specimens are probably trying to grow towards the light source. Turn your terrarium slightly every few days so that the plants all get the same exposure to light, and if they get leggy, move the terrarium to a brighter spot, still out of direct sunlight.
THIS is KILLING Your Terrariums!
FAQ
How do I bring my terrarium back to life?
If your leaves are wilting and the moss looks pale green, open the lid and feel the soil and moss, if it’s dry give it a small spray of water, don’t drown your terrarium it does not need a lot of water. Then put your lid back on and monitor over next few days.
How to fix a dying terrarium?
Keep your terrarium in a stable environment, away from extreme heat or cold. Terrariums are beautiful, rewarding projects, but they do require some attention to thrive. If yours keeps dying, it’s usually a simple fix—just tweak your watering, check your plant choices, and make sure the setup is right.
How do you revive an open terrarium?
There are several troubleshooting steps you can take to revive it. First, check for signs of overwatering or underwatering and adjust your watering routine accordingly. Examine the light conditions and ensure your terrarium is receiving the appropriate amount of light for the plants inside.
What is the lifespan of a terrarium?
Terrarium Lifespan
Though, the average terrarium lasts only about 4 months to 2 years. Perfect conditions are not easy to provide, in fact, they’re almost impossible. And such a terrarium only exists on paper. Bummer right?
Why are terrariums dying?
Few of the main reasons why terrariums are dying include overwatering the plants or soil, using wrong containers for terrariums, mixing plants with different requirements, positioning terrariums in wrong spots. Overwatering plants in the terrarium is one of the most common mistakes and reasons why terrariums start dying.
Can terrarium plants die?
While terrarium plants can die, it is not a common occurrence. There are a number of reasons why a terrarium plant might die, including: too much or too little water, too much or too little light, and improper care. However, if a terrarium plant does die, it is typically because of one of these three reasons.
Can a terrarium get too long?
Yes, if your plants in a terrarium get too long, there’s a higher risk of them dying. That’s because long plants will touch the sides of the terrarium and catch water that can lead to plant rot. If your plants get too long or big, make sure to prune them a little. It’s always a good idea to choose slower growing plants for a terrarium.
How do you care for a terrarium plant?
Solve by placing the terrarium in a bright but indirect light. Leaning to one side means that you need to turn your terrarium once a week or so to allow all parts of a terrarium to get enough sunlight. You can read a terrarium plant pruning guide here. Avoid fertilizing plants too much as it will lead to faster growth.
How do you design a terrarium?
Lay out the plants on the soil to get a feel for the design. Place taller plants at the back of the terrarium and shorter ones at the front. Choose complementary foliage textures and colors. If all of the plants have variegated broad leaves it will look like just one large plant. Remove the plants from the nursery pots and plant them in the soil.
Can you put plants in a closed terrarium?
Even though they like wet soil, they need high heat – which you can’t provide in closed terrarium. If direct light hits the terrarium, it will cook the plants inside. The best suited plants for closed terrariums are mosses, lichen, ferns, some tropical plants. You can find a list of plants for closed and open terrariums here.