The fungus produces a striking, blue, mushroom-shaped fruiting body (basidiocarp), between August and November. The smooth cap measures 5–15 cm (2–6 in)[3] and has a broad swelling in the centre (known as a boss or umbo). The tightly packed, white gills on the underside of the cap contrast well with the blue colour of the fungus; they become more salmon-pink as they age.[4] The solid stipe of the mushroom ranges from 5–10 cm (2–4 in) tall and 1–3 cm wide,[3] and is also blue with a whitish base.[4] The spore print is pink to cinnamon-coloured.[5]