What Is Mushroom Compost?

Does your veggie garden need a little extra oomph? Is your lawn looking a little bit lackluster lately? Or are you just like me and just want to know how you can step up your sustainable living game?

If you answered yes to any or all of these questions, I would suggest you give mushroom compost a go! What is mushroom compost? Where does it come from? How is it different from regular compost? Let’s find out!

What is mushroom compost?

You might be surprised to hear that mushroom compost is actually just a by-product of mushroom farming and doesn’t necessarily contain any mushrooms! It is a wonderful nutrient boost for your garden and can help with water retention as well as break up any heavy clay in your soil. But I will get more into all of the fabulous benefits of mushroom compost later on!

How is mushroom compost made?

Mushroom compost is a by-product of the mushroom-growing industry. It is usually made from a mix of different organic materials like cotton seed hulls, peat moss, soybean meal, corn cobs, manure, hay, gypsum, and straw. All of these organic materials make up the substrate in which mushrooms are grown, but the exact mixture will depend on the grower.

The mushroom farming process starts with dunking large bales of wheat and straw in water. Once the bales are fully saturated, the straw is then run through a chipper to break it up into smaller pieces.

Next, manure and gypsum are blended in with the straw and placed into a hot compost pile (at about 160 degrees Fahrenheit) where it will be turned daily.

This is known as the “hot composting stage” when making mushroom compost and is VERY important to kill off any wheat seeds, pests, or pathogens that might still be hanging around. Did you know that during the “hot stage”, compost bins have been known to spontaneously burst into flames?

Hot compost can even get warm enough to heat hot tubs! I never cease to be amazed by the random composting facts out there.

Once the compost has rested for a few weeks, it can then be pasteurized to kill off any remaining bacteria that might be harmful to plants and humans.

If the compost is going to be used to grow mushrooms commercially (which is often the case), you can mix in mushroom spores at this stage. All in all, the process takes about three to four weeks.

Once the substrate has been exhausted and can no longer be used to grow mushrooms, the by-product can be recycled and resold as fertilizer (usually under the label ‘Spent Mushroom Compost’ or ‘Spent Mushroom Substrate’). This is your mushroom compost!

What's the difference between Mushroom Compost vs. Regular Compost?

Both mushroom-based and regular composts are great plant fertilizers and soil amendments if used properly. But to understand the difference between the two, we first have to talk about how regular compost is made!

You can make regular compost at any time of year using food waste from around your home (yes, you can even compost in your small apartment or compost in the winter with the help of an urban compost bin or compostable trash bag!).

Brown (carbon-rich) items like paper, leaves, and tree bark as well as green (nitrogen-rich) items like old frozen veggies or fruit are all compostable at home.

Shovel Pours Compost into Wheelbarrow — PhotoPin

But there are also some items you should NOT be adding to your compost bin… Avoid adding items like dairy and animal-based food waste like cheese, meat, and fish scraps to your compost bin.

Mushroom composting, on the other hand, requires some specific ingredients you might not have lying around the house (some that might be a bit… smelly in the beginning stages). So depending on what ingredients you choose to use, it might be a bit more challenging to do mushroom composting at home in an indoor space.

I want to also mention that mushroom compost should be viewed more as a soil “treatment” rather than regular food for plants since regular compost is less likely to change the pH of your soil. If you are looking for just a regular plant feed or nutrient booster then I would definitely recommend sticking with regular compost.

So, what makes mushroom compost so special and different? Let’s look at its pros and cons!

The Pros and Cons of Mushroom Compost


  • Mushroom compost is a smart addition to any garden with plants that need a lot of water since it does a fantastic job of retaining moisture. 
  • Mushroom compost is a great amendment to help with drainage in denser soil - like clay!
  • Mushroom compost supplies macronutrients to your soil such as nitrogen, phosphorus, and potassium, as well as micronutrients such as magnesium and iron. 
  • Mushroom compost has a higher level of calcium than regular compost and can be extra beneficial for some crops like tomatoes that do well in calcium-rich soils. Other plants like Hosta, Goldenrod, Salvias, Yarrow, Foxglove, Winter Jasmine, Horse Chestnut, and Boston Ivy all also LOVE mushroom compost.
  • Mushroom compost is known as a slow-releasing compost, this means that it can provide some long-term feeding benefits for your plants!


  • Mushroom compost is a substrate that was exhausted from growing mushrooms, and as a result, the nitrogen content in mushroom compost will be potentially lower than regular compost.
  • Mushroom compost retains a lot of moisture and this can also be its downside! You don't want waterlogged soil.
  • Mushroom compost doesn't mix well with plants that prefer more acidic soils with a higher nitrogen content and this might cause them to underperform. Some examples of plants that don’t like mushroom compost include Blueberry, Camellia, Magnolia, Cranberry, Farn, Lupine, and Holly.
  • Mushroom compost can be quite expensive (bulk mushroom compost typically costs between $30 and $60 per yard).

How to use mushroom compost?

  1. For mushroom compost to work the best, it must be cooled down and cured otherwise the heat might kill any plant roots and/or prevent your seeds from germinating. So, make sure that your compost has had time to cool down.
  2. Like all compost, I would suggest applying mushroom compost to your garden in the early spring or summer. This will ensure your plants are getting the right nutrients when they need it the most. 
  3. You only need one or two inches of mushroom compost spread evenly over the surface of your garden for it to really work its magic! Don’t overdo it.
  4. Like all compost, if your moisture content gets too low then decomposition will slow and the microorganisms in the mixture will go dormant. But like I said earlier, mushroom compost loves water and you can easily add too much moisture to your soil if you aren’t careful. I have seen some gardeners recommend adding mushroom compost to dry soil to avoid this problem.

Where can I find mushroom compost?

You can find mushroom compost at most big box garden stores, as well as plant nurseries, greenhouses, and online suppliers! However, I would suggest you just type into Google, “Where to buy mushroom compost in bulk near me” so you can find a local supplier and avoid paying expensive shipping fees.

But what if I told you that you can make your own mushroom compost? It’s true! Just like regular compost (which you can also make at home), you can make mushroom compost in the comfort of your own home. I love this mushroom compost recipe from InstaMushrooms because it doesn’t require any manure!

Compost bin and wheelbarrow — Photo.Pin

Here is what you will need:

  • 10 lbs of Corn Fodder or Ground Corn Cobs
  • 10 lbs of Straw
  • 2 lbs of Peat Moss
  • 2 lbs of Greensand
  • 3 lbs of Sand
  • Water

All you need to do is mix the corn fodder, straw, and water together and let it sit for 2-3 days. If the straw becomes dry during this process simply wet it again.

Next, fold in peat moss, greensand, sand, and water (if dry) into the mixture (you can also add horse manure or gypsum at this stage).

You can now leave the mixture for 5-6 days to sit and get nice and toasty. Once warm, start to turn the pile every 2-3 days adding more water each time you do.

Depending on the size of your batch, a compost tumbler might make this step a bit easier. But you can also just use an old Tupperware container as a compost bucket.

Keep turning your compost on this schedule for about two weeks straight and your pile should have turned a dark brown color. Let it cool for another week and voila, mushroom compost!

A final word on mushroom compost

Composting can help set you on the right track in your zero waste living journey, and mushroom compost is no exception! There are so many things to love about mushroom compost. To start, it is a great way to reuse a by-product from another industry that might have otherwise gone to waste. It is also a great source of calcium and other nutrients your soil will love.

However, keep in mind that the nitrogen content in mushroom compost might be a bit lower than regular compost. It can also retain too much moisture and oversaturate your mixture if you aren’t careful. As such, mushroom compost should be seen as a soil treatment rather than daily plant feed.

Would you try making or using mushroom compost? Let me know what you think in the comments below! And if mushroom composting isn’t for you, don't worry I have you covered.

Check out my article to learn more about the different types of composting to find out which is right for you. Good luck!!

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