Nine tips for maintaining your closed terrarium

Popular wisdom has it that you don't get something for nothing. If the adage is true for sports records or exams, it doesn't always apply to gardening. The terrarium is the proof. By placing your plants in a jar, you can cultivate a lush tropical garden without wearing yourself out. But there are a few things you should know about maintaining your closed terrarium.

Terrariums are grown indoors. Not very demanding, they are happy in a room with a temperature of between 16 and 27°C.

The location should be bright, so that the plants receive plenty of light. But avoid direct sunlight. Behind glass walls, the temperature is higher than in the open air. Overly strong rays will raise the thermometer and turn your terrarium into a sauna. The magnifying glass effect can also burn leaves. In winter, you can leave your jar behind the glass, but in summer, keep it a little further away to prevent heatstroke and burns.

Once your terrarium is in place, turn it regularly. Plants tend to grow towards the light. By turning your terrarium a quarter turn every month, you'll allow every plant to benefit from the sun and ensure harmonious growth for your garden under glass.

Now that you've brought your terrarium home, it's out of the question to let it vegetate on a shelf. If you do nothing, you risk ending up with a dripping candy jar, or, on the contrary, a dry container.

For the first few weeks, plants go through an adaptation or balancing phase. They have to get used to living together in a closed environment. They must also acclimatize to the temperature and brightness of their new environment.

If water beads up on the outside of the walls, or if condensation prevents you from seeing the inside of the terrarium, it means there's too much humidity. Open the lid for a day to allow excess water to drain away. After 24 hours, close it again and continue your observation. If the humidity remains too high, ventilate again. Condensation should be present, but not fogging or dripping on the outside.

Is your terrarium as dry as Tatooine? It's running out of water. Water it, but remember: it's easier to add water than to remove it. The safest thing to do is to use a spray bottle to spray water at the base of the plants. Give preference to rainwater and avoid tap water. The limescale it contains destabilizes the terrarium ecosystem.

A terrarium takes an average of two weeks to reach equilibrium. After this adaptation period, keep an eye on your mini-world. If you notice a change in hygrometry, restart the process. You should also go through the balancing phase every time you modify an element of your world.

Enclosed terrariums need much less water than potted plants or plants in the ground. Evaporation from the leaves produces condensation, which is captured by the roots. This cycle reproduces itself almost endlessly. When water runs out, you need to water.

Theabsence of condensation is the first sign that your terrarium is thirsty. Other symptoms may also alert you, such as :

When you see any of these signs, water the substrate with your sprayer. Start with a spray or two per plant and leave the terrarium open for 24 hours. Then close the lid. If there's still no condensation, water again. As with adaptation, spray with rainwater. It provides nutrients without harming the balance of the ecosystem. If you don't have rainwater, try demineralized water.

Depending on the species, size and exposure of the terrarium, watering is required two to four times a year. If you're afraid you'll forget, set your own reminder in theMonstera app. This way, you'll receive a notification to prompt you to take a close look at your plants and water them.

Ventilation is your weapon in the fight against high humidity and excessive temperature. When condensation is too heavy and you can no longer see the plants in the terrarium, remove the lid for a few hours, until the drips and mist disappear.

Don't forget to aerate your container when the thermometer exceeds 28°. Even if the plants in your terrarium are heat-loving tropical varieties, they're not immune to heatstroke. By opening the jar completely or leaving it ajar during the day, you can lower the mercury by a few degrees.

Even when enclosed, your plants remain alive. They grow, shed leaves and sprout new shoots. To maintain the harmony of your arrangement and allow air to circulate, you need to prune one to three times a year. Once again, you can program your personalized reminder on theMonstera app to make sure you don't forget, or put off, this key terrarium maintenance gesture.

When pruning, use clean, sharp tools. This limits the spread of disease and helps plants heal. When the opening of your terrarium is too small to fit your hand and pruning shears, even mini ones, get aquarium pliers and scissors.

But what needs pruning? Observe your terrarium to know where to cut. Is your Calathea lancifolia skirting the lid and its stems bent? Cut off any parts that have grown too high above a node. Are the leaves of your Hypoestes phyllostachya touching the glass walls? Remove them! They risk rotting and contaminating all your plants.

Once you've thinned out your mini garden, move on to densification. Pinch the stem ends of creeping species such as ficus pumila and fittonia albivenis. This technique forces the plant to create new branches and maintain its compact habit.

You're probably wondering what to do with yellowed or dried-out leaves. The question is the subject of much debate, with two opposing camps. Some people leave the limbs to die and don't pick them up once they've fallen off. Over time, they decompose and provide the soil with nutrients. Others choose to remove yellowing leaves to preserve the aesthetic appearance of the arrangement and avoid any risk of rotting the rest of the plant.

Pruning, like watering, alters the balance of your closed terrarium. To help plants heal and facilitate adaptation, open your jar for 24 hours after your operation.

The walls of your moist terrarium must be kept clean. This is essential if the plants are to absorb as much light as possible and photosynthesize. A quick wipe with a microfiber cloth is all you need to clean inside and out. Don't add chemicals. You'll kill the plants.

Are you a maniac who can't stand the dirt on the stones, the traces of algae on the walls and the mould residues on your plants? Grab a long-handled paintbrush and clean up the inside of your terrarium.

Even in an enclosed, self-contained environment, you're not immune to pest attacks. Gnats often make an appearance. They won't harm your plants. If their presence annoys you, install a glue trap under the lid to attract and capture them.

Mealybugs and red spiders may take up residence in your Dwarf palm or Ficus microcarpa microcarpa without having been invited. If you notice small white spots on the foliage of your plants, spray the leaves with a mixture of water and black soap. You may have to repeat the operation several times to get rid of them.

Found slugs and snails in the potting soil? Remove them before they devour the leaves. Centipedes and earthworms, on the other hand, are harmless. But they'll be delighted to be free again!

Last but not least, mushrooms may appear. While they add a rather aesthetic wild touch, it's best to remove them as soon as you spot them. They will multiply and invade your composition.

A well-maintained terrarium will last for many years. But not all plants have the same life expectancy. Over the years, you may need to renew certain specimens.

This usually starts with moss, which eventually turns white and dries out. But don't panic! Just remove the old moss and replace it with a new one! Soak your new moss in lukewarm water for a few minutes and plant it in place of the old one. Press it down to ensure success.

Has your Florist's asparagus or bonsai tree given up the ghost? If so, remove them carefully. You can swap your shrub for a plant of the same or a different variety (to select it, read our article on Which plants to choose for a closed terrarium?). This option is highly recommended if the unfortunate plant has died prematurely! Rework the hole to match the dimensions of the root ball and plant the newcomer. Spray the plant with a little rainwater to accelerate rooting.

After each planting, leave your terrarium open for at least a day to regulate humidity.

In a humid environment, certain plants such as ferns, Hypoestes or Aralia (Polyscias fructicosa) will grow rapidly. If their leaves take up all the space, touching the walls or the lid, they've outgrown your terrarium.

The first thing to do is prune the stems and branches back to a volume compatible with that of the terrarium.

But if you've chosen a container that's obviously too small, or you want to give them more space, you can try repotting. Get yourself a larger transparent jar, with an opening wide enough to fit your hand. Place a layer of gravel or clay balls on the bottom, followed by a substrate suited to your plants' needs. Potting soil for green plants will do the trick, but some brands also offer special terrarium potting soil. Remove your protected plants from the old terrarium and plant them in the new one. Install your decorative elements and resume the adaptation phase!