Eupatorium coelestinum, commonly known as blue mistflower or wild ageratum, is a hardy perennial wildflower native to the eastern and central United States, where it grows naturally along streambanks, moist meadows, woodland edges, and roadsides. Typically reaching 1 to 3 feet in height, it forms spreading colonies through its rhizomatous roots, creating dense patches of soft, cloudlike blooms that appear from late summer into fall. The flower heads are composed of fluffy, threadlike, lavender-blue florets that resemble puffs of mist, giving rise to its common name and making it a striking late-season nectar source when many other wildflowers are fading. Its serrated, triangular to ovate green leaves are arranged oppositely along sturdy stems, creating a lush backdrop for the airy flower clusters. Highly attractive to butterflies, bees, and other pollinators, Eupatorium coelestinum is a valuable addition to pollinator gardens, native plantings, and naturalized areas, where it spreads easily and brings a soft, meadow-like charm. Though it thrives in moist soils, it is adaptable to a range of conditions and can tolerate periodic drought once established, making it both ornamental and ecologically important in supporting late-season biodiversity.