A showy wildflower in Illinois, blooming late summer into the fall. Flower heads found at the tops of branching stems are flat-topped clusters of blue, or maybe purple. Each flower head has between 35 and 70 individual disk flowers. Leaves are opposite and toothed at edges. Plant can spread by underground runners. Its favored habitat is moist ground by streams; also found by ditches and low pasture areas. Common in the bottom 2/3 of the state.
When viewed from a distance, may look like a low-lying foggy mist.
I've found it in the fall near woods, in woods, and next to creeks along the Mississippi River.