Kendall County (IL) Forest Preserve District
Thinleaf
Sunflower
(Ten-Petal Sunflower)
Helianthus decapetalus
[C-value
5]
Aster family (Asteraceae)
Blooms
mid-July -
September
The native Thinleaf Sunflower is uncommon in our area. It prefers partial sun or dappled sunlight and moist to slightly-moist rich loamy soil. Habitats include open woodlands, woodland borders, meadows and partially shaded areas along streams. This perenniall is 3-5' tall with erect stems branching occasionally. The lower and middle leaves are opposite, while the upper leaves are alternate. The leaf blades are up to 7" long and 3" across and lance-shaped with long slender tips and sharply toothed, on petioles ½–1½" long. The upper stems terminate in yellow compound flowerheads, 2–3½" across with 8-12 yellow ray florets surrounding numerous yellow tubular disk florets in a central disk.
Thinleaf Sunflower at Pickerill/Pigott Forest Preserve September 15, 2012
Thinleaf Sunflower foliage at Lyon Forest Preserve August 28, 2012
Thinleaf Sunflower at Pickerill/Pigott Forest Preserve July 18, 2017
Thinleaf Sunflower foliage at Pickerill/Pigott Forest Preserve July 18, 2017
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