The distribution of poison-sumac in Wisconsin is intriguing and probably tied to glacial history.  It is common in the Southeast Glacial Plains, especially in the Kettle Moraine region but becomes very rare and local northeast of Lake Winnebago.  It is common in rich swamps in Outagamie and Waupaca Cos. and in the numerous wetlands of the Central Sands and Central Sand Hills.  Populations in the Driftless Area are (or were) restricted to relic bogs (Hansen, 1933), many of which have been destroyed.  Increased collecting of this species has shown that it occurs farther northwest in the state than previously thought and in more counties south of the Tension Zone.

This is a beautiful species, especially in fall, with glossy leaves and ascending branches that have a tropical look.  Although many people claim to have gotten a rash from poison-sumac, it almost always grows deep in wetlands where few hikers venture.  Poison-sumac seems to prefer high-quality wetlands and appears to decline when its associate ash species succumb to emerald ash borer.  Clearly, more research is needed to understand the phytogeography and ecology of this plant.