Varieties deamii, fulgida, spathulata and umbrosa flower late summer to fall. The remaining varieties, palustris, speciosa and sullivantii may begin flowering earlier in the summer but can also bloom in the fall. (Urbatsch & Cox, 2006.)
The following detailed information regarding var. sullivantii is taken from the Journal of the Torrey Botanical Society, July 2007.
"A Rudbeckia fulgida var. sullivantii head took about a month to bloom starting from when the ray florets uncurled to the final disk floret blooming at the apex. In one week involucral bracts uncurled, followed by ray florets extending and then recurving back on top of the bracts. In this time the receptacle became more conical in shape. The perfect, dark purple-brown disk florets matured acropetally, each taking 4-6 days for the corolla to develop. The purple-brown style pushed the pollen up through the corolla tube displaying the pollen, followed by the style bifurcating. If the yellow-orange pollen was not removed from the style branches (via a pollinator), the pollen remained stuck to the tips of the style branches as they separated. Due to the close proximity of each floret in the head, it was possible for pollen to come into contact with the disk floret of the row below. The glabrous style remained bifurcated and developed stigmatic papillae on the upper surface, suggesting receptivity. The style branches continued to curl until the sweeping hairs at their tips almost touch the underside of the branch. The styles remained this way until any lingering pollen turned white (10-14 days). Following this pollen color change, the style soon shriveled inside the corolla tube. This sequence of events means that florets at the base of the head were senescing while florets at the apex were at anthesis. As the head aged, the tips of the ray florets turned a paler yellow color. These greenhouse flower head phenological observations were also confirmed in the natural populations at MNTP."
Scott, Lynne & Brenda Morano-Flores. The Journal of the Torrey Botanical Society. Vol. 134 No. 3 pp. 362-368. 2007. "Reproductive Ecology of Rudbecia Fulgida Ait. Var. Sullivantii (C. L. Boynt and Beadle) Cronq. (Asteraceae) in Northeastern Illinois."
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