Plant name: Smooth ironweed, prairie ironweed
Botanical name: Vernonia fasciculata
Virtues: Easy to grow; blooms late in summer; adds height to flower beds and borders—good background plant; attracts butterflies and bees.
Flowers: Dense clusters of bright purple flowers in late summer to early fall.
Habit: Herbaceous perennial reaching to 5 feet tall. Narrow, unbranched form. Slowly spreads by its roots.
Season: Late summer.
Origin: Wet prairies and marshes of the American Midwest and Great Plains south to Texas.
Cultivation: Prefers full sun and moist to wet soil. Withstands short periods of flooding. Tolerates some share and drier conditions. USDA Zones 4–9.