A closed terrarium is often called a self-sustaining ecosystem because it continuously recycles its own water. Just like nature, a terrarium follows a miniature version of the Earth's water cycle, creating the perfect environment for tropical plants to thrive.

This natural process is one of the reasons closed terrariums require very little watering compared to traditional houseplants.

© Terrart NYC® | All Rights Reserved

Step 1: Evaporation

As the terrarium warms throughout the day, water from the soil, moss, and plants evaporates into the air.

Plants also release moisture through a process called transpiration, adding humidity to the ecosystem.

Step 2: Condensation

As moisture rises and meets the cooler glass walls, tiny water droplets begin to form.

This condensation is often seen in the morning and is a sign that the ecosystem is functioning properly.

Step 3: Precipitation

As water droplets grow larger, they slide down the glass and return to the soil.

This process mimics rainfall in nature and helps keep the ecosystem hydrated.

Step 4: Absorption

The soil, moss, and plant roots absorb the water, using it for growth and survival.

The cycle then begins again.

Why This Matters

Because water is constantly recycled, most closed terrariums only need watering every 1–3 months, depending on the vessel and environmental conditions.

A healthy water cycle helps:

• Maintain humidity
• Support plant growth
• Reduce maintenance
• Create ecosystem balance
• Keep moss healthy and vibrant

Signs the Water Cycle Is Working

• Light condensation that comes and goes
• Slightly moist soil
• Healthy green moss
• Vibrant tropical plants
• Little to no standing water

At Terrart NYC, the water cycle is one of the most important concepts we teach during our workshops and DIY Terrarium Kit experiences. Understanding how moisture moves through a terrarium helps owners maintain healthier ecosystems for years.