Mushroom compost is the organic matter left after the mushroom growers have finished the mushroom growing process. It is mainly made up of chicken manure, straw, and sometimes peat moss.
The mushrooms grown from the mushroom materials can be good for consumption. If the straw substrate was for edible mushrooms from a mushroom farm, there is a good chance the mushrooms growing in the compost will also be edible.
What Happens if you Eat Compost Mushrooms?
Lots of things are edible but no longer good to eat. Should we eat mushrooms that we find in mushroom compost? Like plants and other things that grow in our garden, if we know for sure what it is and what is good to eat, then it is safe. If in doubt, do not eat it.
Mushrooms are part of the kingdom of Fungi and exist with a whole assortment of other organisms that range from essential for life to deadly if inhaled. But like plants in our gardens, mushroom spores need to be planted and cultivated to bring forth mushrooms.
Most of the fungi that exist do so below the surface of the soil and never break the ground. They move fertilizers around and add water retention to the soil, making gardeners’ lives easier. But given water, the right nutrients, and the correct light and season, many other species of fungi will bring forth a flush of fruit.
If you specifically added mushroom spores to your compost and know the varieties of mushrooms that will grow in that environment, you have much more control over the results of the flush. Many strains of mushrooms can be safely cultivated in a home compost pile or directly in vegetable gardens and between plants.
Other mushrooms may result from animal urine or foreign introductions to your compost. While these mystery mushrooms should not be eaten, they can help break down straw and manure in your compost pile and provide nutrients to your plants. Mushrooms help gardeners by speeding up the breakdown of compost piles.
Never eat wild mushrooms growing in mushroom compost that you can not identify. Never eat mushrooms that are off in color or texture. Only expect to have edible mushrooms growing in your compost if you recently:
- Inoculated the compost with edible mushrooms
- Used mushroom compost from an edible mushroom farm
- Threw unused edible mushrooms into the compost pile
If none of those events occurred, then the wild mushrooms in your compost are probably not edible to anyone but an experienced mushroom forager. Bury all unknown mushrooms deep in your compost pile before the spores are released to avoid spreading potentially poisonous mushrooms throughout your yard.
Can Mushrooms Grow in Compost Yard Litter?
It is possible for fungi to grow in your compost, on leaf litter, and throughout your garden beds. Like worms, when there is frequent water, a build-up of moisture, and plenty of organic materials to get nutrients from flushes of mushrooms will follow.
Within a few weeks of putting leaf litter or a layer of peat on your compost and around your plant beds, certain types of mushroom spawn will grow and fruit. Several of these types of mushrooms are good for food and can easily be grown, harvested, and eaten.
Leaf litter, bales of straw, and fine compost can make excellent mushroom substrates for these varieties of fungi:
- Wood Blewit (Clitocybe Nuda) – These attractive blue and pink mushrooms are good for food but take over a year to have their first flush. It grows naturally on organic yard waste and common compost ingredients. It helps speed up the composting process and yields delicious earthy, savory, and dense mushrooms for the dinner table.
- Shaggy Ink Cap (Coprinus Comatus) – A specialty mushroom, it only lives a short time and begins to break down as soon as it is picked. It has a delicious flavor like asparagus but no shelf life. They will grow on active compost with high soil quality but die off when the pile temperatures rise too high.
- Wine Cap Stropharia (Stropharia Rugosoannulata) – One of the easiest and most resilient mushrooms grown on compost, this fungus has a rich, delicious flavor. It feeds on hardwood litter and can help break down harder compost material. In well-mulched-vegetable beds, they can increase crop levels.
- Almond Mushroom (Agaricus Subrufescens) – Close cousin to high-quality mushrooms like button and portabella mushrooms, it is a delicious fungus that grows best on fine and finished compost. It can grow when you keep the soil moist and produces well on various compost materials. They commonly give three to five flushes.
Do Mushrooms from Compost Make You Sick?
Eating mushrooms from compost can make you sick. Lots of factors go into the cultivation of mushrooms, and the chance of contamination from other types of bacteria and fungi is always a risk. Some mushrooms can be poisonous; other types may be covered in bacteria or other compost-related impurities.
While not all mushrooms in compost will make you sick unless you consciously grow mushrooms, you shouldn’t eat what grows on your pile. Seeds, spores, critters, and bacteria all live in compost, and any combination can make you sick. Metal and salt content build-up, especially soluble salts, can also make you ill, even if the mushroom is safe to eat.
How To Grow Mushrooms In Compost?
It turns out it is easy to grow mushrooms while your compost is either actively breaking down or sitting finished waiting to be used. Mushrooms can deplete nutrients that plants want later, but a rich compost should have more than enough, and slow-release fertilizer can be added later.
- Sterilize – In order to successfully grow mushrooms, it helps to eliminate all competition. The best way to give your spores a level playing field is to let the compost heat up to 160℉ for a hot compost pile and kill the weed seeds, other fungi, and harmful bacteria that have colonized. After the temperature drops, innoculate the pile and try to keep new seeds out of the compost pile for a couple of weeks.
- Mushroom Soils – Make sure that the top of the compost is mushroom soil. Layers of mushroom compost, straw, or manure will be needed for the spores to innoculate and spread. The mushroom growth rate will depend on the nutrients in the compost, garden soil, and the amount added inoculating.
- Keep Compost Moist – It is important in the mushroom farming industry to always add misters to spray the compost and keep it moist. Unlike plant growth which can be hindered by wet roots, oyster mushrooms and other edible varieties love water. They even break up clay in a couple of weeks of growth so you can water freely even in the worst soils.
- Monitor Flushes – Eventually, much like potted plants, the mushroom house will push up, and you will begin to see fruits emerging. The variety of materials mushrooms grow in makes it hard to tell exactly when it will flush, but temperature changes and light increases can usually activate the first flush. Most edible fungi have multiple flushes, so keep looking for more after the first is harvested.
- Harvest the Mushrooms – Bales of wheat straw are great for harvesting mushrooms not just because of their nutrient content but also because their height makes them easy to harvest. If your compost is low, you may have to bend or crouch to harvest the flushes. Harvest when ripe, the signs of maturity depend on the type of mushroom you are growing and the mushroom substrates they are growing in.
Benefits of Mushrooms in Compost
In almost all cases, the presence of mycelium and fungi in your compost and soil is good. With the rare exceptions of poisonous mushrooms that are dangerous to pets and kids, most mushrooms are either harmless or extremely helpful. Below are some ways mushrooms help our compost.
| Mushroom Type and Stage | Benefit | How to Increase | Warnings |
| Spores | Create more Fungi | Innoculate appropriate mushroom substrate | Some spores may lead to undesirable mushrooms |
| Mycelium | Breaks up soil and moisture retention | Add more mushroom substrates for expansion | Impossible to completely remove from the soil or compost without sterilization |
| Flushes | Create mushroom fruit that can breakdown hardwoods and hazardous materials | Optimal nutrients and environment for large, fast, healthy flushes | Poisonous and undesirable mushrooms may appear as well |
| Edible | Food source for people and animals | Innoculate compost with correct spores | Cross-contamination can lead to illness |
| Composting | Breaks down waste extremely fast | Add plenty of moisture and break up large materials | Some mushrooms that compost well can spread fast or cause problems with pH balance |
| Poisonous | Has unique properties | Learn about the mushrooms in your compost | May be eaten by a pet or animal or a misinformed adult. |
Spores
The most direct way to create more mushrooms and add the fungi you want to your compost pile is with spores. Spores can be brought into a pile naturally or added intentionally. Spores can increase the presence of good fungi to a level that bad spores cannot compete with.
Mycelium
The network that fungus uses to navigate the subterranean world is mycelium. Mycelium aerates the soil in an endless quest to find more nutrients and establish symbiotic trade networks with all other organisms. This white floss running through the soil also improves dirt structure and adds water retention capabilities as well.
Flushes
These large explosions of mushrooms are fungi’s most productive stage in terms of decomposition powers. The mushrooms unleash a slew of chemicals that activate enzymes, melt, or just break down organic materials faster than anything else. Mushroom flushes allow spores to be released so that even more fungi can live and feed on decay.
Edible
During the flush is when edible mushrooms can be harvested. They benefit the compost piles by adding productivity during times of dormancy. Compost piles sit unused and age over the winter in most temperate climates, and the right design can utilize that time for food production. Edible mushrooms provide the same underground benefits with the added element of a reliable food source.
Composting
Nothing breaks organic materials down faster than fungus. From hardwoods and stumps to stubborn cloth or all-natural twines, mushrooms are what break down the things bugs and bacteria can’t process. It is easy to move fungi in your compost to other piles for inoculation and to various garden beds. When soil runs out of nutrients for mushrooms, then the flushes stop, but the soil enhancements last for several months.
Poisonous
Even though poisonous mushrooms can be dangerous, they also represent a chance to learn and understand mushrooms in your area better. The sight of some poisonous mushrooms is enough to drive off certain grazers and critters who understand its dangers and can save your compost pile from disruption. If you remove the mushroom caps before the spores spread, the underground benefits of fungi can be gained without the dangers of pollination. Hopefully, future generations of mushrooms won’t be poisonous.
If you do have poisonous mushrooms or any wild unidentified mushroom that could be dangerous growing in your compost, do not leave them there. If you have children or pets, they could accidentally ingest it and get sick. Remove the mushrooms and bury them deep in your compost before it has produced spores to prevent accidental damage and further spreading of their spores.