Flat

Going flat

For the vast majority of mushrooms, a flat shape is a sign of maturity or old age:

1. Porcini (Boletus edulis): Starts life as a dense little ball. In its prime it is convex. And when the mushroom gets very old (its tube layer turns dark olive and soft), the cap opens fully and becomes perfectly flat. Old, flat porcini like these are not worth picking: they are often crumbly and may contain toxins from protein breakdown.

2. Parasol mushroom (Macrolepiota procera): Its life cycle is a perfect illustration of the transition. From a shaggy, ball-shaped "drumstick" it turns into a huge flat disc (a parasol) up to 30-40 cm across, often with a small umbo in the center.

3. Brittlegills (Russula): Most brittlegills pass through the ball-shaped stage very quickly and by day 2-3 of their life are already completely flat "saucers" growing in the moss. Their brittle flesh suits this shape perfectly.

4. Death cap (Amanita phalloides): An adult, old death cap has a perfectly flat olive-green cap (up to 15 cm across) that looks like a perfect brittlegill (but the stem has a ring and a volva!).

The risks of flat mushrooms

M.Ya. Zerova reminds us of the forager's golden rule: if a mushroom's cap has become completely flat, the mushroom is old.

The only exception is brittlegills, which open up very quickly. In all other cases (porcini, aspen boletes, slippery jacks, Agaricus mushrooms), a flat shape shows that the flesh has gone soft and lost its flavor, and most likely the mushroom is already heavily infested with insect larvae (maggots). Mushrooms are best picked at the "convex" stage.