Thinleaf Sunflower (Helianthus decapetalus)

Thinleaf  Sunflower (Helianthus decapetalus)

Thinleaf sunflower (Helianthus decapetalus) is a native perennial of eastern and central North America, including Wisconsin. It usually grows three to six feet tall and often forms loose colonies through its rhizomes. The bright yellow flower heads are two to three inches across, each with eight to twelve rays around a brownish central disk. They appear in open clusters from late summer into early fall and draw a wide mix of pollinators.

The leaves are thin‑textured, lanceolate to ovate, and rough to the touch. They range from three to six inches long and one to three inches wide. Upper leaves are mostly opposite; lower leaves may shift to alternate. Stems are slender, smooth or lightly hairy, and branch near the top. Thinleaf sunflower favors partial shade to dappled sun and grows best in moist, well‑drained soils along woodland edges, thickets, and shaded slopes. Its late‑season bloom and colony‑forming habit make it a steady contributor to pollinator support in naturalistic plantings and restoration work.

Sources:

Flora of North America – Helianthus decapetalus

USDA Plants Database – Helianthus decapetalus

Illinois Wildflowers – Thinleaf Sunflower

Minnesota Wildflowers – Helianthus decapetalus

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