The similar-looking but not-recommended Coprinopsis variegata
differs in that it grows on decaying hardwood and the cap usually has less of an overall white color. It may cause gastrointestinal distress and/or adverse reactions when consumed with alcohol, even in the space of several days. The inedible Coprinopsis lagopus
has a similarly elongated cap but differs in that it is much smaller (under 4 cm broad when fully expanded). It has a very delicate fruiting body that lasts only a few hours before dissolving into black ink. A number of other poisonous or inedible white mushrooms that have warty or scaly caps are superficially similar. They differ in that they do not turn inky/black when old, and/or do not have a blackish spore deposit.