Northern Prairie Wildlife Research Center
Cup-plant (Silphium perfoliatum)
- Family: Aster (Asteraceae)
- Flowering: July-September.
- Field Marks: The cup formed where each pair of opposite leaves comes together on the stem and the strongly square stems readily identify this species.
- Habitat: Low woods, around ponds, wet meadows, along streams.
- Habit: Coarse perennial herb with thickened rootstocks.
- Stems: Erect, branched or unbranched, square, usually smooth, up to 10 feet tall.
- Leaves: Opposite, simple, ovate, pointed at the tip, united at the base with the opposing leaf to form a cup, coarsely toothed, rough to the touch, up to 1 foot long, up to 6 inches broad.
- Flowers: Many crowded together into heads, with numerous heads per plant; each head up to 3 inches across, subtended by elliptic to ovate, ciliate bracts, composed of 20-30 yellow rays and a central yellow disk.
- Sepals: 0.
- Petals: Yellow, some united to form rays, others united to form tubes that comprise the central disk.
- Stamens: 5.
- Pistils: Ovary inferior.
- Fruits: Achenes obovoid, winged, up to 1/2 inch broad.
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