How Often to Water Closed Terrariums: A Comprehensive Guide

How Often to Water Closed Terrariums: A Comprehensive Guide


Closed terrariums are a captivating way to bring a piece of the natural world into your home. These miniature ecosystems enclosed in glass containers create a self-sustaining environment for plants. One of the most crucial aspects of maintaining a healthy closed terrarium is knowing how often to water it. In this comprehensive guide, we will explore the factors that influence watering frequency, the signs of overwatering and underwatering, and provide practical tips for keeping your closed terrarium thriving.

Understanding Closed Terrariums

Before delving into watering schedules, it's essential to understand the unique characteristics of closed terrariums:

  1. Sealed Environment: Closed terrariums are designed to be sealed or nearly sealed containers. The closed environment recycles moisture, creating high humidity levels and minimizing water loss.

  2. Self-Sustaining Ecosystem: Closed terrariums are meant to be low-maintenance, self-contained ecosystems. Once properly established, they should require minimal intervention.

Factors Influencing Watering Frequency

Several factors impact how often you should water your closed terrarium:

  1. Terrarium Size: The size of your terrarium affects its water needs. Larger terrariums may require less frequent watering because of the increased volume of air and moisture inside.

  2. Plant Selection: Different plant species have varying water requirements. Choose plants that are well-suited to the closed terrarium's high humidity environment. Some popular choices include ferns, mosses, and polka dot plants.

  3. Substrate Choice: The type of substrate used in your terrarium also plays a role in moisture retention. A well-draining mix with good moisture-holding capacity is essential.

  4. Container Type: The type of container you use can affect humidity levels. Airtight containers create a more stable environment, requiring less frequent watering compared to containers with small openings.

  5. Light Exposure: The amount of light your closed terrarium receives affects its water needs. Terrariums placed in direct sunlight will have higher evaporation rates, while those in low light conditions may require less frequent watering.

Signs of Overwatering

Overwatering can be detrimental to the health of your closed terrarium. Signs of overwatering include:

  1. Foggy Glass: If the glass remains persistently foggy or covered in condensation, it's a sign that excess moisture is trapped inside. Try to aim for fog less than 1/3 of the terrarium container. 

  2. Plant Wilting or Yellowing: Overwatered plants may show signs of stress, such as wilting, yellowing leaves, or rotting roots.

  3. Mold Growth: Excessive moisture and inadequate ventilation can lead to mold growth, which can harm the terrarium's aesthetics and affect plant health.

  4. Musty Odor: A musty or unpleasant odor inside the terrarium may indicate overwatering and the development of mold or mildew.

Signs of Underwatering

Underwatering can also negatively impact your closed terrarium. Signs of underwatering include:

  1. Dry Soil: The soil in the terrarium will appear visibly dry and parched.

  2. Wilting Plants: The plants will show signs of dehydration, with leaves becoming limp and drooping.

  3. Soil Separation: If the soil starts to separate from the glass container, it may be too dry.

  4. Low Humidity: The humidity levels in the terrarium may drop significantly.

Establishing a Watering Schedule

The key to successful closed terrarium care is finding the right balance between overwatering and underwatering. Here are some steps to establish a proper watering schedule:

  1. Observe Your Terrarium: Regularly monitor the conditions inside your closed terrarium. Check for signs of overwatering or underwatering.

  2. Perform the "Condensation Test": Condensation on the glass is a reliable indicator of humidity levels. If you notice minimal or no condensation, it may be time to water. If condensation is persistent, postpone watering.

  3. Stick to a Routine: Create a regular watering schedule, but be flexible. While closed terrariums require less frequent watering, the actual schedule will depend on your specific terrarium's conditions.

  4. Use the "Finger Test": Insert your finger into the soil to determine moisture levels. If the soil feels dry about an inch deep, it's time to water.

  5. Invest in a Hygrometer: A hygrometer is a valuable tool for measuring humidity levels in your closed terrarium. It can provide an accurate indication of when watering is necessary.

  6. Water Sparingly: When you do water your closed terrarium, use a spray bottle or a small watering can to provide a gentle, even distribution of moisture. Avoid overwatering, as excess water can disrupt the terrarium's balance. Remember to use distilled water so that the container remains visibly clear without any calcium deposit streaks.

  7. Adjust Based on Season: Keep in mind that your closed terrarium's water requirements may change with the seasons. During the cooler months, less frequent watering may be necessary, while in hot weather, you may need to increase watering frequency.


Closed terrariums offer a mesmerizing way to enjoy nature indoors, and understanding how often to water them is vital to their success. By considering the factors that influence watering frequency, recognizing signs of overwatering and underwatering, and following a structured watering schedule, you can maintain a healthy and thriving closed terrarium. With proper care and attention, your closed terrarium will continue to flourish as a beautiful, self-contained ecosystem in your home.

Back to blog