Terrariums are much like miniature hothouses. More precisely, a terrarium can be thought of as replicating the environment of out own planet earth. One of the climatic features of our wonderful is phenomenon of continuously recycle water that is trapped in the atmosphere. This water cycle is what sustains life, as we know it. There is no end to this continuous cycle and moisture present in the air is always in motion.
A properly constructed terrarium enclosure can be thought of as the layers of the atmosphere that surrounds the earth. Moisture that is trapped in the atmosphere does not vent off into space but is confined between the atmospheric layer the surface of the earth.
Over ninety seven percent of our water is found the oceans, with the oceans making up over seventy percent of the earths surface. Ocean water is constantly undergoing the process of evaporation. Simply put, evaporation is the transformation of water into a gas and the heat of the sun drives the evaporation process. As the water gas vapor rises, the process of condensation takes over.
The visible evidence of condensation can be in the formation of clouds at various levels in the atmosphere. The cooler air of the upper atmosphere causes the gas to cool forming water droplets. These water droplets are suspended in the air, producing various types of clouds. At very high altitudes, the condensed water will freeze forming ice crystals.
When the atmosphere becomes saturated with moisture, the moisture will return to the surface of the earth as precipitation. Examples of precipitation are rain, snow, hail, even fog and sleet. Once precipitation reaches the surface, the cycle of evaporation, condensation and precipitation repeats itself.
The water cycle in a terrarium is very similar to the process that occurs in nature. The evidence of this continuous cycle can be seen in several ways. In a properly constructed terrarium enclosure, moisture will appear as condensation on the inner surfaces of the enclosure. Gravity will cause the condensed moisture to run back down to the soil. Moisture also will condensate on the surface of the plants in a process referred to as canopy interception.
One of the drawbacks to growing certain species of house plants in a pot is controlling the amount of moisture in the soil. The ambient air conditions can vary widely from room to room and even from one side of a room to another. Temperature and humidity in the average house is hard to control. I have always found it a challenge to maintain a proper balance of moisture in my potted plants. Too much or too little water spells trouble for most potted plants.
For anyone who has struggled with indoor plants, a terrarium allows us to grow and enjoy a wide variety of plants. The secret of course is the terrarium water cycle. Water that is added to the terrarium tends to remain in that environment and is recycled from the soil to the air and back to the soil.
Part of the terrarium water cycle involves the plants through the process of transpiration where water is expelled from the plant. Continuing the cycle, the water expelled from plant cell evaporates, condenses and precipitates all in the confines of your terrarium.
Now the water cycle in a terrarium will not produce a deluge of rain or a thunderstorm. Nevertheless, a terrarium allows us to witness first hand the delicate balance that exists in nature, a balance that keeps the earth cool and hydrated. The same process that occurs in your terrarium makes life on this beautiful planet possible.