Silphium perfoliatum aka Cup Plant

Silphium perfoliatum, or cup plant, is a tall perennial. It belongs to the daisy family, Asteraceae. Its native range spans southeastern Canada and the central and eastern United States. It grows in prairies, meadows, thickets, and open woods. It also grows beside streams, ponds, and lakes. This plant loses its leaves at the season's end.

Garden plants reach 4–8 feet (1.2–2.4 metres) tall. Some sources give heights near 10 feet (3 metres). The spread is about 1–3 feet (0.3–1 metre). Thick, smooth stems have four sides and stand upright. They branch near the flowers and may have reddish tones. Large green leaves grow in pairs along the stems. Their rough surfaces and coarse teeth give a bold texture. The upper leaf pairs join around each stem. These cups catch water, which draws birds to the plant. Lower leaves may wither before the flowers open.

Yellow flower heads grow in branched clusters above the leaves. Each head measures about 3–4 inches across. Yellow rays surround a darker yellow disc of small flowers. Bloom dates range from June through October across the sources. Bees, wasps, and flies visit for nectar and pollen. Butterflies and hummingbirds also visit the flowers. Winged seeds form from the outer ray flowers. Fruits appear from July to September, and goldfinches eat the seeds. These birds also drink from the leaf cups.

Cup plant grows best in full sun and rich, moist loam. It accepts some shade and tolerates clay and wet soil. Established plants withstand some drought, but dry spells can damage leaves and buds. Sources list USDA zones 3–9, though Chicago gives 3–7. The RHS rates it H7 for cold hardiness. Seed-grown plants may wait until their second year to flower. Gardeners can also divide plants, but deep roots make established clumps hard to move.

Its size suits meadows, native gardens, and large borders. It can form a tall backdrop beside other perennials. Heavy seed production can make it spread too freely. Wind may topple stems; shaded plants may need stakes. Serious pest and disease problems are uncommon, though red aphids sometimes attack leaves. PFAF lists no known edible uses or hazards. It records past medicinal use by Indigenous North American peoples. Its pregnancy warning calls for qualified guidance before medicinal use.