Species Native to Missouri
Common Name: giant ironweed
Type: Herbaceous perennial
Family: Asteraceae
Native Range: Eastern United States
Zone: 5 to 8
Height: 5.00 to 8.00 feet
Spread: 3.00 to 6.00 feet
Bloom Time: August to September
Bloom Description: Rose purple
Sun: Full sun to part shade
Water: Medium to wet
Maintenance: Low
Suggested Use: Naturalize, Rain Garden
Flower: Showy
Tolerate: Deer, Wet Soil
Culture
Easily grown in average, medium to wet soils in full sun to part shade. Although it is often seen growing in the wild in moist soils, with tolerance for periodic flooding, it performs quite well in cultivation in average garden soils. Plants generally grow taller in moist soils. Overall plant height may be reduced by cutting back stems in late spring. Easily grown from seed. Remove flower heads before seed develops to avoid any unwanted self-seeding. This species of ironweed tends to hybridize with some other native ironweeds, which can sometimes complicate plant identification.
Noteworthy Characteristics
Vernonia gigantea, commonly called giant ironweed, is one of the tallest of the ironweeds, growing to as much as 10’ tall in a growing season. It is native from New York to Missouri south to Georgia and Louisiana. In Missouri, it typically occurs in low woods along streams, valleys, low thickets, swamp borders, prairies and meadows (Steyermark). This is an upright perennial that typically grows 5-8’ in cultivation on stiff, leafy stems which branch at the top. Lanceolate to lanceolate-ovate leaves (to 10” long) have irregularly serrated margins. Composite flowers, each with dense, fluffy, rose-purple disks (rays absent), bloom in corymbose cymes from late summer into fall. Flowers give way to rusty seed clusters. The source of the common name for vernonias has been varyingly attributed to certain “iron-like” plant qualities including tough stems, rusty-tinged fading flowers and rusty colored seeds. Notwithstanding its toughness, the plant is, with the exception of its attractive flowers, a somewhat unexceptional ornamental. Flowers are very attractive to butterflies. Synonymous with and formerly known as V. altissima.
Genus name honors William Vernon (d. c. 1711), English botanist who collected in Maryland in 1698.
Species name means unusually tall or large.
Problems
No serious insect of disease problems.
Uses
Naturalize in cottage gardens, wildflower meadows, prairies or native plant gardens. Also effective as a background plant for borders. Good for areas with moist soils.