Thinleaf Sunflower (Helianthus decapetalus)
A native perennial of eastern and central North America, including Wisconsin, thinleaf sunflower typically grows 3 to 6 feet tall, forming loose colonies through rhizomes.
Its bright yellow flower heads measure 2 to 3 inches across, each with 8 to 12 ray florets surrounding a central brownish disc. Flowers bloom in loose clusters from late summer into early fall, attracting a wide range of pollinators.
Leaves are lanceolate to ovate, thin-textured, and rough to the touch. They range from 3 to 6 inches long and 1 to 3 inches wide. Upper leaves are arranged oppositely, while lower leaves may be alternate. Stems are slender, often smooth or slightly hairy, and branch gracefully near the top.
Thinleaf sunflower thrives in partial shade to dappled sun, favoring moist, well-drained soils in woodland edges, thickets, and shaded slopes. It is a valuable species for pollinator support and naturalistic plantings in restoration and garden settings.