Try www.fungi.com or just google mushroom kits. The first site I mentioned is quite well known. You can buy "logs" you can grow inside or stuff to innoculate logs you grow outside. We have done both and they both were productive. JoAnn
We grow shiitake mushrooms on logs outside (easy to do in the south east with our high humidity.)They don't take up very much space if you use the stack method you can stack 14-16 logs in a 5'x5' space. Unless you buy already inoculated logs this is the wrong time to get started. The trees have to be fresh cut before the sap is rising (winter or early spring). NC A&T has a program for growing mushrooms here is a link http://www.ces.ncsu.edu/nreos/forest/woodland/won-20.html We buy our spawn from field & forest http://fieldforest.net/index.html Her is a picture of our mushrooms in May