I would say it depends on which/what spell you are trying to do. Since a mushroom in one spell can mean something else in a different spel l. However, I did find this website on what mushrooms are used for and how they can be used in magic . ( But, I'm sure someone else has a better link and knowledge for mushrooms, but I hope that I helped you )
Link : http://www.badwitch.co.uk/2008/09/mushrooms-and-fungi.html ( Mushrooms)
I hope this helps you learn more about mushrooms.I know it did for me.
By mushroom, I sure you hope you don't mean as in magic mushroom, aka LSD. No one should be taking any sort of drug, or psychedelic for spiritual purposes. They're just hallucinations, and it is dangerous.