I recently was in a sand prairie/savanna remnant in St. Joseph County, Indiana when I stumbled into a healthy population of Stachys hyssopifolia (I later found out that Keith Board had found this population years before). This mint is found at various locations in states along the east coast of the United States, but it is also disjunct in the Midwest/Great Lakes region, specifically in Michigan, Indiana, Illinois, and to a lesser extent in Missouri. In 25% of the states in which it occurs, Stachys hyssopifolia is considered a species of conservation concern.
Stachys hyssopifolia has an interesting ecological distribution. Those who have compiled the National Wetland Plant List seem to think of this species as a pure wetland plant, as it is ranked as OBL or FACW in all regions in which it occurs. That would mean that it is almost always found under wetland conditions but that it is occasionally found in uplands. Many of the references I checked state that this species is found in moist soils, often near lake margins, and also in bogs. This is of course true, but it is also found in dry acid soils of prairies and savannas. Regardless of wetness, it seems that Stachys hyssopifolia tends to require acidic conditions.
Stachys hyssopifolia, like some other members of the genus, is said to have edible tubers.