Plants treated by Steyermark (1963) and some other botanists as M. ringens var. minthodes (Greene) A.L. Grant appear instead to represent interspecific hybrids between M. ringens and the closely related M. alatus. The name M. ×minthodes Greene has been applied to such plants, which appear to be at least partially fertile and are variable morphologically. Putative hybrids tend to have the leaf blades tapered or angled at the base, but lacking a true petiole. They also have calyx lobes intermediate in length between those of the two parents. Because the parents frequently grow in mixed populations, hybrid individuals probably are relatively common but undercollected.