Composting is already one of the best ways to recycle organic matter and enrich soil, but did you know that mushrooms can take your compost pile to the next level? Fungi, particularly mycelium—the vast underground network of mushroom roots—play a crucial role in breaking down complex organic materials, accelerating decomposition, and improving soil health.
What is mushroom compost?
Mushroom compost is a nutrient-rich organic material that results from the breakdown of various growing substrates used in mushroom cultivation. It typically consists of materials like straw, sawdust, manure, gypsum, and other organic matter that has been colonized by mushroom mycelium. Once mushrooms have completed their growth cycle, the leftover substrate—known as spent mushroom substrate—is repurposed as compost.
Mushrooms and their mycelium are nature’s decomposers, capable of breaking down lignin, cellulose, and even certain toxins in the soil. Unlike bacteria, which thrive on simpler organic matter, fungi excel at decomposing tough plant materials like wood chips, cardboard, and straw. This makes them especially useful in compost piles that contain a lot of woody or fibrous material.
Recent research highlights the practical benefits of spent mushroom compost in improving soil health. A study by Khalil et al. (2024)1 found that it not only enhances plant growth and yield but also helps suppress harmful plant pathogens, making it an excellent tool for disease control in vegetable crops.
How to add mushrooms to your compost
1. Choose the Right Mushroom Species – Oyster mushrooms and Wine Cap mushrooms are excellent choices for composting. They aggressively colonize organic material and improve soil structure.
2. Add Mushroom Blocks or Spawn – If you’ve grown mushrooms before, you can add spent mushroom blocks directly to your compost. Otherwise, sprinkle sawdust spawn or grain spawn into layers of carbon-rich material like wood chips or straw.
3. Keep Conditions Ideal – Mushrooms prefer moisture and airflow. Keep your compost damp but not soggy, and turn it occasionally to ensure aeration.
4. Let Mycelium Work Its Magic – Over weeks or months, mycelium will break down tough materials, creating a nutrient-rich, fungal-dominant compost that is perfect for garden beds and plant health.
Golden Oyster mushrooms growing in the North Spore compost pile.
What are the benefits of mushroom compost?
• Faster Breakdown of Organic Material – Mycelium accelerates decomposition, reducing overall composting time.
• Healthier Soil Microbiome – Fungal networks attract other soil microbes, including fungi, bacteria and invertebrates, which improve soil biodiversity, leading to healthier plants and increased nutrient availability.
• Improved Soil Structure – Mycelium binds soil particles together, enhancing water retention and aeration.
• Natural Disease Suppression – Some fungi produce compounds that suppress harmful soil pathogens, reducing the risk of plant diseases.
By incorporating mushrooms into your composting routine, you not only reduce waste but also create a thriving, nutrient-dense soil ecosystem that benefits your garden and the environment. So why not let fungi do the heavy lifting and turn your compost into a powerhouse of fertility?
Want to dive deeper?
Research & further reading:
1. Khalil, S., et al. (2024). Practical applications of spent mushroom compost in cultivation and disease control of selected vegetable species. SpringerLink. https://link.springer.com/article/10.1007/s10163-024-01969-9