Unlike other oyster varieties, the King Oyster doesn’t usually produce a shelf like formation, but instead produces a mushroom with a round cap and a defined stem.
The cap usually unrolls with age, becoming flat and eventually uncurled. If grown indoors with minimal fresh air and low light levels, the mushroom will grow a fat tall stem and a tiny cap, while lots of fresh air and light will produce a mushroom with a small stem and large dark cap.
King Oysters can be quite large, sometimes producing single fruits weighing well over one pound.