Mushrooms Growing in Your Compost Bin – Is This Normal?

Opening up your compost bin to find mushrooms poking up through the soil can be surprising, but it’s actually quite common Mushrooms thriving in the moist, organic environment inside compost bins are a natural part of the decomposition process. But what do mushrooms growing in your compost mean? Are they harmful? And what should you do about them? This guide covers everything you need to know about managing fungi in compost

Why Mushrooms Grow in Compost Bins

Mushrooms are actually the fruiting bodies of certain fungi The ideal conditions for mushroom growth happen to be the same warm, humid, shaded environment created inside compost bins Specifically, mushrooms tend to flourish when

• Moisture levels are high
• Temperatures range from 60-75°F
• There’s indirect sunlight
• Airflow is present
• Organic matter, leaves, grass, wood chips, etc. are abundant

As microorganisms break down the organic waste, fungi release enzymes to help decompose tough materials like lignin and cellulose. They also grow threadlike mycelium networks which distribute nutrients and moisture throughout the compost. When conditions are right, like after heavy rain, the mycelium may fruit as mushrooms.

Common Mushrooms in Compost

Various mushrooms species will colonize compost piles depending on the materials present and how decomposed they are. Common types include:

• Button, cremini, and portabella mushrooms – These appear on finished compost at the end stage of decomposition

• Wine cap stropharia – Grow on wood chips, sawdust, straw as it breaks down.

• Blewits – Decompose grass clippings, leaves, garden waste in mid-stage decomposition.

• Shiitake and oyster – Break down newly dead or freshly cut wood in early stages.

• Inky caps – Enjoy active compost piles but die off at peak heating.

Benefits of Mushrooms in Compost

Contrary to concerns, mushrooms growing in compost piles are actually beneficial:

• Speed up decomposition – Fungi break down lignin, cellulose and woody matter more quickly.

• Improve soil health – The mycelium networks enrich soil structure, help retain moisture, and provide nutrients.

• Release nutrients – As mushrooms break down, they add minerals like copper, potassium, and phosphorus to the compost.

• Indicate proper conditions – Mushrooms signify your compost has the right moisture, airflow, and materials to facilitate natural decomposition.

Risks and How to Control Mushrooms in Compost

While mushrooms are not necessarily harmful, take these precautions:

• Remove unidentified mushrooms as some types are poisonous. Don’t allow children or pets access.

• Turn compost piles frequently to disrupt fungal growth and improve airflow.

• Add more nitrogen-rich greens like grass clippings to balance the carbon in woody browns.

• Introduce red wiggler worms to break up mycelium networks as they tunnel.

• Maintain temperatures between 130-140°F to destroy mushrooms and their spores.

• Lime raises pH which most fungi don’t tolerate.

• Make sure the pile isn’t over-saturated. Allow it to dry out between waterings.

Growing Edible Mushrooms in Compost

For the adventurous composter, allowing mushrooms to grow in your compost opens up the opportunity to cultivate edible varieties right at home. Some choices include:

• Blewit mushrooms – Have an earthy flavor and beautiful blue, pink, and lavender caps. Grow well on semi-composted leaves, grass, and yard trimmings.

• Wine caps – Large, nutty mushrooms that grow easily on woody plant debris. Hardy and good for beginners.

• Almond mushrooms – A sweeter relative of the button mushroom. Plant chunks of spawn in finished compost beds.

• Shaggy ink caps – Mild, with an asparagus-like taste. Enjoy warm active compost piles. Must harvest promptly before they liquefy.

When growing edible mushrooms, always verify mushroom identification before consuming any you aren’t 100% certain about. Consider joining a local mycological society if you need help identifying mushroom species.

Troubleshooting Excessive Mushroom Growth

While some mushrooms are normal, prolific growth could indicate underlying issues:

Problem: Mushrooms cover the entire surface of the pile.

Cause: Too much moisture, not enough air.

Solution: Turn the pile to dry and aerate it. Add bulking agents like wood chips.

Problem: Mushrooms keep returning after removal.

Cause: Established mycelium network.

Solution: Frequently turn the pile to disrupt fungi. Maintain hot compost temperatures.

Problem: Mushrooms have a foul odor.

Cause: Anaerobic conditions, not enough nitrogen.

Solution: Add nitrogen-rich greens, turn pile to introduce more air. Check moisture levels.

Problem: Mushrooms only in one section.

Cause: New materials were added.

Solution: Quickly mix any new additions thoroughly into the center of the pile.

When to Worry About Compost Mushrooms

Consult an expert if you notice any of these potentially toxic mushrooms:

• White gilled mushrooms that bruise blue – Could be death cap or destroying angel mushrooms.

• Bright red mushrooms with white spots – Possibly the toxic fly agaric.

• Rapid mushroom growth after flooding/heat – May be poisonous amanitas.

• Mushrooms near pet waste – Might be toxic Chlorophyllum species.

• Mushrooms on treated lumber – More likely to be poisonous.

Exercise caution and never handle mushrooms with bare hands. Dispose of unidentified mushrooms safely in an outdoor refuse pile until an expert can confirm they are not toxic. Always supervise children and pets around open compost piles where mushrooms are growing.

In most cases, the presence of mushrooms signifies healthy, natural decomposition. With some basic maintenance and safety measures, mushrooms growing in your compost bin are no cause for concern. For avid composters, cultivating gourmet mushroom varieties at home is an exciting new gardening adventure!