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The tip of a smooth ironweed central stem bears a cluster (a corymb) up to 4" in diameter of magenta composite flowerheads that is quite densely packed in a flat or (sometimes) domed inflorescence. The branches of the inflorescence (but not the stem) may be lightly fuzzy with small hairs. Each flowerhead is 3/4" across and contains 10-30 magenta disk florets, each with five lobes and a very prominent, divided style with curled tips (the stigmas) and five stamens appressed to the base of the style; ray florets are completely absent. The bracts that cover the underside of the flowerheads are green or purplish brown, flattened, appressed, and rounded at their tips, imbricated like fish scales with white, cobwebby hairs around their edges. The fruit is a naked seed with an attached tuft of white hairs (actually, scales). To sort out the Jackson Park ironweeds: (1) if both leaves and stem are densely covered with fine white hairs, the leaves are about 3-4 times longer than wide, and each flowerhead has more than 30 disk florets, it's Missouri ironweed (V. missurica). (2) If both leaves and stems are hairless, there are less than 30 disk florets, and the leaves are narrow (typically a half inch or less; about 6-10+ times longer than wide), it's smooth ironweed (V. fasiculata). (3) If the stems and leaves have only short hairs, there are less than 30 disk florets, and the leaves are about 2" wide and 4-6 times longer than wide, it's tall ironweed (V. gigantea).

Vernonia

Vernonia fasciculata

smooth ironweed [Blooms: Jun-Sep]

Tall ironweed's inflorescence is a flat-topped panicle arising from the tip of the central stem; it is 6-16" across, open and spreading. There are 10-30 disk florets in a tall ironweed flowerhead. The base of the flowerhead is covered by several series of dark colored, broadly oval appressed bracts (phyllaries), often with fine hairs around their edges. The disk florets have tubular, trumpet-like corollas with five recurved lobes; ray florets are absent. Tall ironweed has a much more "open" composite flowerhead than the other ironweeds in Jackson Park, with the trumpet bases of the disk florets easily visible. The fruits are naked, gray or brown, bullet-shaped seeds with a tuft of both short and long tawny or pale purple hairs. To sort out the Jackson Park ironweeds: (1) if both leaves and stem are densely covered with fine white hairs, the leaves are about 3-4 times longer than wide, and each flowerhead has more than 30 disk florets, it's Missouri ironweed (V. missurica). (2) If both leaves and stems are hairless, there are less than 30 disk florets, and the leaves are narrow (typically a half inch or less; about 6-10+ times longer than wide), it's smooth ironweed (V. fasiculata). (3) If the stems and leaves have only short hairs, there are less than 30 disk florets, and the leaves are about 2" wide and 4-6 times longer than wide, it's tall ironweed (V. gigantea).

Vernonia

Vernonia gigantea

tall ironweed [Blooms: Jul-?]

At the tip of a Missouri ironweed stem, a corymb of composite flowerheads (the inflorescence) is produced. The stems of the inflorescence are also covered in fine white hairs and usually reddish brown in color. Individual flowerheads are magenta and rayless; ray florets are completely absent. Flowerheads contain 32-60 disk florets, each 1/2-3/4" across, which have rounded or broadly angled bracts (phyllaries) with sharp tips, dull green or reddish brown in color, that are layered like fish scales around the base. To sort out the Jackson Park ironweeds: (1) if both leaves and stem are densely covered with fine white hairs, the leaves are about 3-4 times longer than wide, and each flowerhead has more than 30 disk florets, it's Missouri ironweed (V. missurica). (2) If both leaves and stems are hairless, there are less than 30 disk florets, and the leaves are narrow (typically a half inch or less; about 6-10+ times longer than wide), it's smooth ironweed (V. fasiculata). (3) If the stems and leaves have only short hairs, there are less than 30 disk florets, and the leaves are about 2" wide and 4-6 times longer than wide, it's tall ironweed (V. gigantea).

Vernonia

Vernonia missurica

Missouri ironweed [Blooms: Jul-Oct]