How to tell White knight from Death cap

The cap is 4–10 cm across. Young caps are conical to convex with an inrolled margin, then flatten out around a small, low boss, often with a wavy edge. In the white knight the margin is smooth; a ribbed margin points more to the chemical knight of birch woods.

The colour is white to cream, sometimes with a pale yellow tinge. With age the centre turns ochre or yellowish brown, and old caps develop ochre spots. The surface is dry, matt and smooth, and stays dry even in rain.

The death cap's cap is 5–15 cm across, hemispherical when young, then opening out flat.

Its colour ranges from olive green and yellowish green to greyish and almost white, which is exactly what makes it tricky to identify. The surface is smooth and a little slimy in wet weather, with a characteristic pattern of darker fibres radiating from the centre. The margin is even, with no striations.

The gills are white, later pale yellowish, thick, fairly distant and of unequal length. They are clearly notched just before the stem, and their edges are finely toothed.

The spore print is white. Pink or chocolate-brown gills mean a field mushroom relative; gills running down the stem point to a funnel.

The gills are crowded, thin and free, meaning they don't touch the stem. They're white and may turn creamy with age, sometimes with a faint pinkish tinge, but they never turn chocolate brown.

It never has the chocolate-brown gills of a mature Agaricus. The gap between gills and stem is clear. In young mushrooms a white, membranous veil covers the gills completely.

The stem is 3–8 cm tall and 0.8–1.5 cm thick, cylindrical, sometimes slightly wider at the base. It's white to pale yellowish brown, powdery at the top, finely fibrous lower down, and slowly browns when handled.

There is no ring, no veil remnants and no bag-like volva at the base. If you find such a sac, you're holding an amanita.

The stem is slender, 7–15 cm tall and 1–2 cm thick. It's cylindrical and swells at the base into a characteristic club-shaped bulb wrapped in a membranous, sac-like volva. That volva is the main diagnostic feature.

It's whitish green, often with a faint, banded snakeskin pattern. A well-developed white ring, left over from the veil, hangs in the upper third. Below the ring the surface is faintly scaly.

The flesh is white and firm, thick in the cap, and doesn't change colour noticeably when cut (some authors note a faint pink tint). The taste is acrid and burning, with bitterness.

The flesh is white and doesn't change colour when cut, and that's the treacherous part: none of the safety signs foragers usually rely on work here. It's thin and brittle in the cap, thicker and firmer at the base of the stem.

It doesn't darken in the air, not after a minute and not after an hour. Don't let "lovely white flesh" reassure you: the white flesh of the death cap is exactly where amanitins are most concentrated.

The smell is strong and unpleasant: sharp like radish, with a sickly sweet note of honey and a mealy edge when cut. Young specimens smell less, mature ones can be smelt from a distance. A nauseating chemical smell, like cooked beetroot or coal gas, belongs more to its relatives, the chemical knight of birch woods and the gassy knight (Tricholoma inamoenum).

Fresh, it has a faint smell that's easy to miss, and young ones barely smell at all. Mature mushrooms pick up a slightly sickly-sweet note, like wilted honey or stale dough.

That smell isn't strong enough to warn an inexperienced forager. Like other poisonous amanitas (the fly agaric, the panther cap), the death cap smells faint and nondescript, so it gives you no warning at all, which is one more treacherous trait. Only rotting mushrooms smell any stronger.