Do You Need to Add Fertilizer to Your Sealed Terrarium?

Do You Need to Add Fertilizer to Your Sealed Terrarium?

Creating a sealed terrarium is like crafting a miniature ecosystem inside a glass container. It's a fascinating way to bring a piece of nature into your home. But once you've set up your terrarium, you might wonder whether you need to add fertilizer to keep your plants healthy and thriving. Let's explore this topic and consider some organic alternatives, including the benefits of worm castings.

Understanding the Sealed Terrarium Ecosystem

A sealed terrarium is a self-sustaining environment. The plants inside your terrarium release moisture, which condenses on the walls and trickles back into the soil, mimicking the natural water cycle. This closed system provides a stable habitat for your plants, recycling nutrients within the terrarium. Because of this unique setup, adding fertilizer to a sealed terrarium is not always necessary. Too much fertilizer can actually harm your miniature ecosystem by encouraging excessive growth (which is not ideal for smaller terrariums) or causing mineral build-ups that can damage the plants. 

When to Consider Fertilization

While sealed terrariums generally do not require additional fertilization, there are exceptions. If you notice your plants are growing slowly or their leaves are pale, it might indicate a nutrient deficiency. In such cases, a very light application of fertilizer can help. However, it's crucial to use the right type and amount to avoid upsetting the terrarium's delicate balance.

Organic Alternatives: The Magic of Worm Castings

If you decide that your terrarium could benefit from a nutrient boost, consider organic alternatives to traditional fertilizers. Worm castings, also known as vermicompost, are an excellent option. These are essentially worm droppings, which might not sound appealing at first, but they're a gold mine for plants. Worm castings slowly release nutrients into the soil, providing a steady supply of organic matter without the risk of fertilizer burn or chemical buildup.

Worm castings are rich in beneficial microorganisms and enzymes that can help improve soil structure and promote healthy plant growth. They also contain water-soluble nutrients, making them easily accessible to your terrarium plants. Using worm castings in your sealed terrarium not only feeds your plants but also enhances the soil's overall health, supporting a thriving mini-ecosystem.

How to Use Worm Castings in Your Terrarium

Integrating worm castings into your terrarium is simple. When setting up your terrarium or during occasional maintenance, sprinkle a thin layer of worm castings on top of the soil before planting. If you're adding them to an established terrarium, gently mix the castings into the top layer of the soil. Remember, a little goes a long way in a sealed environment.


In conclusion, while adding fertilizer to a sealed terrarium is not usually necessary, there can be situations where your plants need a little extra nourishment. Opting for an organic alternative like worm castings can provide a safe and natural nutrient boost. This approach ensures that your terrarium remains a vibrant and healthy miniature world, with minimal intervention. Embrace the simplicity and elegance of your sealed terrarium, and enjoy the beauty of nature indoors.

By understanding the needs of your terrarium and choosing the right products, you can ensure your little ecosystem thrives for years to come. Whether you're a seasoned terrarium enthusiast or just starting out, remember that sometimes, less is more. With the right care and occasional organic boosts, your sealed terrarium will be a source of joy and tranquility in your home.

Back to blog