How long does it take to grow a mushroom? by MVMushrooms | Apr 11, 2018 | 0 comments A How long does it take to grow a mushroom? It takes about 60 days from the start of composting before we begin to harvest a mushroom. Submit a Comment Cancel replyYour email address will not be published. Required fields are marked *Comment * Name * Email * Website Save my name, email, and website in this browser for the next time I comment. Currently you have JavaScript disabled. In order to post comments, please make sure JavaScript and Cookies are enabled, and reload the page. Click here for instructions on how to enable JavaScript in your browser.