Terrarium Up Close - Irrigation

While light is the hardest concept to grasp,

we find that the topic on irrigation the most misunderstood. Yes, terrariums are indeed self-sustaining, but that is to a very big “to-a-certain-extent”. So many times, we have met clients who assumed that they are self-sustaining and simply ignore the importance of watering them. Which resulted in a one-way street for the mosses in the terrarium.

Yes, even though there are a lot of truths to terrarium being self-sustainable, and not needing to be watered as frequently as a typical houseplant, we cannot simply use that as a reason to excuse ourselves from monitoring the terrarium and water them when necessary

The whole idea of a self-sustaining terrarium is that the condensation caused by the greenhouse effect and evaporation of the plants and substrate will be collected at the inner side of the glass jar. And once they get dense enough, the water droplets will fall right back into the soil. This is definitely true, and it’s the basis of what makes them a terrarium in the first place.

However, for the terrariums we do here at InOut Atelier, the water that is returned back to the mosses are not enough. Mosses do not have roots like your typical household plants, where they will grow and stretch to reach for the water source. Mosses on the other hand absorb water through their green leaves. The water that slips right back into the mosses are mainly around the inner circumference of the terrarium, and not evenly spread among the mosses. Which means, the rest of the mosses are not getting the amount of water that they ought to be.

Aren’t they suppose to be self sustainable?

The whole idea of a self-sustaining terrarium is that the condensation caused by the greenhouse effect and evaporation of the plants and substrate will be collected at the inner side of the glass jar. And once they get dense enough, the water droplets will fall right back into the soil. This is definitely true, and it’s the basis of what makes them a terrarium in the first place.

However, for the terrariums we do here at InOut Atelier, the water that is returned back to the mosses are not enough. Mosses do not have roots like your typical household plants, where they will grow and stretch to reach for the water source. Mosses on the other hand absorb water through their green leaves. The water that slips right back into the mosses are mainly around the inner circumference of the terrarium, and not evenly spread among the mosses. Which means, the rest of the mosses are not getting the amount of water that they ought to be.

Therefore, it is paramount that the mosses are carefully monitored to ensure that they are moist and damp at all times.

What is the frequency of watering? And how much to water?

This is probably the most commonly asked question with regards to watering needs. Our short answer is once every two weeks. But the best indicator to tell if the terrarium needs to be watered is to touch and feel if the mosses are damp or dry. If they feel slightly on the dryer side. Then, it’s best to water them. The reason for us telling clients once every two weeks is so that they can develop a habit to monitor their terrarium at least twice a month. We don’t think that is too much of a commitment to ask for. Use a spray pump to water, do not pour water into the terrarium because the last thing we want with watering our terrarium is to have a case of over watering. Spritz the mosses evenly till they are moist, but not wet.

What happens when I overwater them?

We should always avoid issues such as this that are within our control. That is why, using a spray bottle to spritz the terrarium is always the best way to water them. Do not pour water into the terrarium to prevent over watering. The excess water will be collected at the bottom of the terrarium and it will be difficult to remove. Furthermore, the excess water runs and filter through many layers of organic matters before settling at the bottom. This stagnant water probably will have bacterial. And it’s not a good idea to have that in a humid enclosure with limited ways of removal.

If your terrarium is a relatively small one, you can wrap your hands in a plastic bag, put your hand, together with the plastic bag into the terrarium, and tilt your terrarium at a steep angle, almost 180 degrees. Hold and push the terrarium content upwards to prevent the mosses and substrate to fall, this will allow the excess water to drain out while keep the subtract intact. This is not the most ideal method, but this is the best one for this situation.

What type of water should I use to water the terrarium?

The short answer: use non-chlorinated water, rain water or distilled water.

Tap water can work, only if you leave it out overnight to allow the chlorine to evaporate. Chlorine is a gas at room temperature, and in water it's a "volatile solute" meaning its molecules are diffused in the water, and it will escape into the air over time. The amount of time needed varies with air and water temperature. Heating or boiling the water will speed the process.

In general, chlorine is harmful to mosses, and they are used to kill mosses where needed. The chlorine content in our local tap water is safe for our consumption. But they may not be for the mosses. You will not be able to see drastic effect upon watering them immediately, but they are definitely harmful to a certain extent. We find that prolong watering with chlorinated tap water will result in the mosses bleaching overtime, giving a pale white or yellow outlook.

In summary…

We hope that we’ve addressed the common misconception with terrariums and we see more people finding joy in growing them, not losing more hope when their terrarium fails.