It's true that a greenhouse may not seem like an optimal location in which to go about your mushroom growing at first sight. But this is a fallacy. A green house can easily be adapted to the task of growing mushrooms and doing so can involve something as simple as covering the greenhouse with a canopy of plastic. So long as you screen out the light your mushrooms should do perfectly well. Another thing that you're going to have to see to if you want to grow mushrooms in your greenhouse is ensuring that temperatures remain stable. Mushrooms don't like too much of a variation in temperature and so this is something that you must try to avoid. If you can keep the temperature above around fifty degrees F and below sixty degrees F or so, your mushrooms should do just fine.

Now, another thing that you need to know about mushrooms is that if you want them to grow reasonably well, or indeed even to grow at all, you can't begin by planting them in mud. This is because fungi, which is what mushrooms are, don't grow in soil. Their organism is essentially made up of quite different materials from those of plants, and this means that mushrooms will refuse to grow unless planted in a medium that is rich in nitrogen. Such a medium is called a growth medium, and it can either be produced yourself with some effort, or can be bought in a store. If you intend to create the growth medium yourself, bear in mind that this can take some effort and is hardly worthwhile unless you intend growing a fairly large quantity of edible mushrooms.

On the other hand, for those in the initial stages of mushroom growing or those without much experience I would recommend a readymade growth medium. This will be more than adequate to your needs until you gain more experience, or alternatively, wish to expand productivity. At that stage, you can always begin producing your own growth medium to reduce the costs of your mushroom growing.