After the Mushrooms: Compost

One of the wonderful things about growing mushrooms (aside from the mushrooms themselves) is the byproduct at the end of the cycle – the compost. Contrary to popular belief, blue oysters and shiitakes do not grow on manure, yet the growing medium is still a valuable source of nutrition. The base for the oyster mushrooms is pasteurized straw, to which other amendments are added, as well as the spawn (ie. seed).

Once the mushrooms have gone through 3 or 4 growing cycles, the mushrooms have completed their growing, yet the straw base still has lots of value for the soil. We store the spent medium in huge compost piles, which are turned occasionally to promote good composting. After several months, the end product is a beautifully rich, spreadable compost – ideal for garden topdressing.

There are high levels of microrhyza, for optimum root growth, for starters. The pH is 7.6, and it has a natural nemacidal effect on soil pests. When used as a top dressing, the earthworms love it! They come up to the soil surface and drag the compost down, effectively incorporating it into the soil structure. After even one season of topdressing, the improvement to the soil structure is highly visible. My vegetable and flower gardens have never grown so well, or been so healthy! And because of the composting process, and the fact that the straw was initially pasteurized before growing mushrooms, there are no weed seeds (something that cannot always be said from using animal manure, especially if it is not properly seasoned…)

Last weekend, spring took a holiday and it was a sleety, blustery day. Regardless, our son, Phillip, spread mushroom compost over one of our fields where we will be growing open-pollinated corn varieties this summer.

Here the compost is being loaded into the spreader…
(click on the picture to enlarge it)

…which will be used to broadcast it over the field

This is what it looks like up close:

We now have several repeat customers who come each spring to get their compost for their gardens. Some are neighbours who use it on their vegetable and flower gardens, others are professional gardeners who recognize the landscaping value of this product. I’m just happy that I have an endless supply of it…and the gardens are grateful, too!


3 responses to this post.

  1. I love hearing about businesses that generate a revenue streams from their by-products … expecially a by-product that is great for the environment in general and, more particularly, the local eco-system. Keep up the good work.


  2. Posted by Mary Ann on March 18, 2013 at 4:20 pm

    you have great info here — can you also grow button mushrooms in this type of soil or does it have to be manure based?


    • Hi Mary Ann! I am not 100% positive, but I believe that manure is a key component of growing button (agaricus) mushrooms. There are many, many different types of growing mediums for the many, many varieties of mushrooms that can be grown. We chose the oysters because it worked out best for us. We are using our own wheat straw, which helps keep costs down, but more importantly, ensures clean and healthy straw.


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