Inedible

Three reasons a mushroom is inedible

David Arora and M.Ya. Zerova name three main factors that put a mushroom in the inedible category:

The most common reason. A classic example is the Bitter bolete (Tylopilus felleus). This mushroom looks very much like porcini or a birch bolete, smells wonderful and is never wormy. But its flesh is so intensely and unbearably bitter that even one small piece that ends up in the shared pot will hopelessly ruin the whole dish — it will be impossible to swallow. The bitterness doesn't go away with cooking; it only gets stronger.

This group also includes some brittlegill species with an incredibly hot, peppery taste that burns the tongue.

A huge number of mushrooms are perfectly safe chemically but have the texture of wood, leather or cork.

For example, the Tinder fungus (Fomes fomentarius) or the Birch polypore (Fomitopsis betulina). They grow on tree trunks and are so hard that cutting them often takes a saw or an axe. Their flesh can't be cooked or chewed, but they are often used for medicinal purposes (as a powder or decoction).

Some mushrooms give off such a disgusting smell when cooked that they kill any appetite. For example, the Sulfur knight (Tricholoma sulphureum) has a strong smell of coal gas and tar. Even though it isn't deadly poisonous, the very thought of putting it in your mouth is repulsive. This group also includes the Common stinkhorn (Phallus impudicus) at the mature stage (because of its smell of rotting meat).