Why Do You Put Moss Under Soil in a Terrarium? Detailed Guide

Terrariums are becoming popular for indoor gardening. They are small glass containers with plants inside, creating a little nature space at home. One important part of setting up a terrarium is using moss under the soil. It may seem odd, but it helps the plants in many ways.

So, why do you put moss under soil in a terrarium? Moss helps keep the terrarium moist, improves drainage, and supports plant health. It keeps the right humidity, stops roots from rotting, and creates a perfect environment for plants. This simple layer of moss is very important for keeping the terrarium healthy.

In this article, we will explain why do you put moss under soil in a terrarium, showing how it helps plants grow and keeps the terrarium in good condition.

What is Moss and How Does It Benefit Terrariums?

Moss is a small plant that grows in wet and shady places. Moss has several helpful properties. It absorbs and retains water, keeping terrariums humid. It also cleans the air by taking in carbon dioxide and releasing oxygen. Additionally, moss helps prevent overwatering by distributing water evenly and stopping soil from getting too wet.

Moss greatly benefits terrariums. It enhances their natural beauty with its lush green color and soft texture. It maintains humidity, ensuring plants grow better, and creates a stable, healthy environment for them. Moss is also low maintenance and only needs occasional misting to stay fresh. 

Common Types of Moss for Terrariums

Sheet Moss: Flat and creates a green carpet for large areas.

Cushion Moss: Forms round, bumpy shapes for added texture.

Java Moss: Thrives on rocks or wood in humid spaces.

Reindeer Moss: Unique shapes and colors for decoration.

Mood Moss: Bright green, soft, and ideal for shaded spots.

Interesting Facts About Moss

With over 12,000 types of moss, this versatile plant can hold up to 20 times its weight in water and live for 3-5 years in a terrarium when cared for properly. Simple yet powerful, moss is essential for keeping terrariums healthy and beautiful, creating the perfect mini garden! 

Why Do You Put Moss Under Soil in a Terrarium?

Moss is more than just a pretty addition to terrariums; it plays essential roles that help plants thrive.

Drainage Layer Function: Moss, especially sphagnum moss, works as part of the drainage system. It prevents soil from compacting at the bottom and creates tiny air pockets, allowing water to flow instead of stagnating.

Water Management: Moss acts like a sponge, soaking up excess water and slowly releasing it when needed. This helps keep the terrarium humid and prevents overwatering problems.

Root Health Benefits: Moss creates a barrier between soil and drainage materials, preventing soil from washing down. It provides a healthy space for roots to grow and contains natural antimicrobial properties to protect them.

Nutrient Benefits: As moss decomposes, it releases nutrients and creates slightly acidic conditions that many plants prefer. It also improves soil structure and adds trace minerals.

Practical Construction Benefits: Moss keeps soil from falling into the drainage layer, acts as a filter, and organizes terrarium layers. This makes building and maintaining a terrarium much easier.

Prevents Root Rot: By improving aeration and moisture balance, moss helps prevent waterlogged roots. Its natural antifungal properties protect roots from harmful organisms while allowing them to stay hydrated.

Maintains a Clean Environment: Moss filters debris, reduces algae and mold risks, and keeps soil from muddying the drainage layer. This helps maintain a neat, healthy terrarium.

Moss not only looks great but also supports the entire ecosystem inside a terrarium, ensuring plants grow well in a clean and balanced environment.

How to Use Moss Under Soil in a Terrarium

Preparation

Choosing Moss: To start, use sphagnum moss, which can be either dried or living. It’s important to make sure the moss is clean and free of dirt or any debris. Avoid moss that shows signs of mold or unusual discoloration. For the best quality, purchase moss from trusted garden stores or suppliers.

Preparing Moss: If you are using dried moss, soak it in distilled water for about 20–30 minutes to rehydrate it. After soaking, gently squeeze out the excess water so that the moss is damp but not dripping. Break any large clumps into smaller pieces and remove any foreign objects like twigs or dirt that may be mixed in with the moss.

Layering the Moss

Layering the Moss: Begin by adding a 1–2 inch layer of drainage material at the bottom of your terrarium. Options include gravel, charcoal, or LECA (Lightweight Expanded Clay Aggregate). Spread this drainage material evenly across the base to ensure proper water flow.

Adding the Moss Layer: Next, lay ½ to 1 inch of the prepared moss over the drainage material. Spread it evenly to cover all the areas without leaving gaps. Press down gently to eliminate any air pockets and create a smooth, flat surface. You can add a little extra moss around the edges to ensure full coverage.

Adding Soil: Once the moss is in place, carefully add your potting soil on top. Be gentle, as you don’t want to compress the moss layer too much. Keep the moss and soil layers separate, ensuring they don’t mix. Add enough soil to accommodate the plants you plan to use in the terrarium.

Maintaining Moss

Regular Checks: It is important to regularly check the moss layer to ensure it remains damp but not soggy. Watch for any signs of mold or yellowing moss, which may indicate poor conditions. Make sure water drains properly and that soil isn’t mixing into the moss layer.

Watering Tips: When watering, pour water gently over the top and allow it to seep through. Avoid overwatering, as this can cause the moss to become too saturated and compact. Keep the humidity levels balanced in the terrarium to maintain the health of the moss and plants.

Long-Term Care: Over time, moss may break down and need to be replaced. Check periodically to make sure the drainage is still functioning properly. Keep the terrarium well-ventilated, and clean the glass to prevent algae buildup.

Extra Tips for Success

Use a chopstick or a similar tool to check that the moss and soil layers remain separate and intact. Consider adding activated charcoal to reduce any unwanted odors in the terrarium. Adjust the thickness of the moss layer based on the size of your container—larger terrariums may need more moss for optimal results.

Finally, take notes or pictures of your layering process, which will be helpful for future reference or adjustments.

Must Read: Aquascaping Plants That Do Not Need Soil

Common Mistakes to Avoid When Using Moss Under Soil

Using Too Much or Too Little Moss

If you use too much moss (over 1 inch thick), it can hold too much water and stop drainage. This can lead to soggy soil and root problems. On the other hand, if you use too little moss (less than ½ inch), it won’t filter water or manage moisture properly. The best moss layer is usually between ½ to 1 inch thick.

Overwatering and Its Effects

Watering too much can squash the moss layer and cause problems. It can lead to root rot, mold, and compacted soil. Too much water also stops the moss from filtering water correctly. Water only when the top of the soil feels dry, and make sure the terrarium drains well.

Choosing the Wrong Type of Moss

Using the wrong moss, like outdoor moss or decorative moss, can bring pests or cause poor drainage. These types of moss may break down quickly or not hold moisture well. Always choose fresh, sphagnum moss made for terrariums to ensure it works well and lasts longer.

Alternatives to Using Moss Under Soil in a Terrarium

Activated Charcoal Layer

Activated charcoal is a popular alternative to moss in terrariums because it effectively filters water, absorbs toxins, controls odors, and prevents bacteria growth. It does not break down and lasts a long time. However, it has a few drawbacks. It doesn’t retain moisture like moss, making it less ideal for keeping plants hydrated. Additionally, charcoal can be messy to work with and is more expensive than moss.

Pebbles/Gravel

Pebbles or gravel are often used in terrariums to provide excellent drainage. They don’t decompose, are easy to clean, and are very affordable. These materials allow water to flow freely, helping to prevent waterlogging. On the downside, pebbles and gravel don’t retain moisture, which means they won’t support the same moisture regulation that moss offers. Additionally, they can be heavy when used in large terrariums.

LECA (Lightweight Expanded Clay Aggregate)

LECA is a lightweight material that provides excellent drainage and aeration for plant roots. It’s reusable and long-lasting, making it an eco-friendly option. However, LECA is more expensive than other materials and doesn’t retain moisture as effectively as moss. It can also float if it becomes waterlogged, which can affect the stability of the terrarium.

Horticultural Sand

Horticultural sand is another drainage solution for terrariums. It prevents soil from compacting, drains well, and is inexpensive. However, like pebbles, it doesn’t retain moisture. It also doesn’t provide any nutrients for plants, which means it needs to be combined with other materials. Over time, sand can compact, reducing its effectiveness in drainage.

Comparison with Moss

Conclusion

In conclusion, Why Do You Put Moss Under Soil in a Terrarium? Using moss under the soil in a terrarium is great for your plants. Moss keeps moisture in, helps good microbes grow, and filters the water. It also stops the soil from becoming too packed and helps prevent root rot.

Moss makes the air in the terrarium more humid, which is perfect for tropical plants. By using moss, your terrarium will stay healthy and look beautiful.

FAQs

Why do you put moss under the soil in a terrarium?

Moss helps with water absorption, keeps the soil healthy, prevents root rot, and improves air circulation for better plant growth.

What are the benefits of using moss in a terrarium?

Moss retains moisture, filters debris, controls humidity, prevents soil erosion, and provides nutrients as it decomposes.

How does moss prevent root rot in terrariums?

Moss absorbs excess water, keeping the soil well-drained and preventing the roots from sitting in water, which could cause rot.

Can moss improve soil aeration in a terrarium?

Yes, moss creates tiny air pockets, allowing oxygen to circulate better, which supports healthy root development and stronger plant growth.

What types of moss are best for terrariums?

Common moss types for terrariums include sheet moss, sphagnum moss, cushion moss, and reindeer moss, each offering unique moisture-retention benefits.