Butomus is the only known genus from the plant Household Butomaceae, native to Europe and Asia. It’s considered invasive.

Butomaceae

The Butomaceae household was recognized by the majority of taxonomists for a plant family; it may be called the”flowering-rush household”.

The APG II system, of 2003 (unchanged from the APG system, 1998), also recognizes such a household, and puts it at the order Alismatales, in the clade monocots. The household counts one species, Butomus umbellatus.

In the ranks of household and order, this is the same positioning as in the Cronquist system. But, Cronquist assumed a much smaller order and assigned the order to subclass Alismatidae, in course Liliopsida [=monocotyledons]