Culture: Easily grown in average, medium to wet soils in full sun. Although it is mostly 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 species of native ironweeds, which can sometimes complicate plant identification.
Noteworthy Characteristics: Vernonia missurica is best distinguished from other ironweeds by the usually greater number of disk florets per flower and by the hairy stems and leaf undersides. It is native from southern Ontario, Michigan and Nebraska south to Alabama and Texas. In Missouri, it typically occurs in moist open ground along streams, wooded swamps, low meadows, prairies, fields and waste places throughout most of the State except the western Ozarks and unglaciated prairie regions (Steyermark). This is an upright perennial that typically grows 3–5’ (less frequently to 6’) tall on stiff, leafy stems which branch at the top. Narrow, lance-shaped to narrow-ovate leaves (to 7” long) have serrate margins. Composite flowers, each with dense, fluffy, magenta 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 variably 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. Genus name honors William Vernon (d. c. 1711), English botanist who collected in Maryland in 1698. Specific epithet is in reference to the Missouri River.
Problems: No serious insect or disease problems.
Garden Uses: Naturalize in cottage gardens, wildflower meadows, prairies or native plant gardens. Also effective as a background plant for borders.
Perhaps the showiest of Ironweeds, Vernonia missurica’s bright magenta, rayless composite flowers have over 30 disk florets (other Vernonia species typically have less). Also unlike other Ironweeds, Missouri Ironweed has many dense white hairs on the underside of its leaves, often lending them a silvery appearance.
A member of the Sunflower family (Asteraceae), Missouri Ironweed blooms late summer to early fall. It is a great way to attract pollinators because it serves as a late-season nectar source. The caterpillars of some moths feed on Ironweed species, including Grammia parthenice (Parthenice Tiger Moth), Perigea xanthioides (Red Groundling), and Papaipema cerussata (Ironweed Borer Moth). Like milkweeds (Asclepias spp.), ironweeds (Vernonia spp.) are bitter to the taste, so herbivorous animals like deer and cattle will avoid consuming it.
This species is found most often near the central and southern Mississippi River valley. Missouri Ironweed will thrive in recently disturbed areas, as well as undisturbed high quality habitats. Although Missouri Ironweed is common in some states, it is endangered in Ohio. This plant’s dominant reproductive method is to spread by rhizomes, and readily self-hybridizes with other Vernonia spp. like Vernonia fasciculata (Common Ironweed), Vernonia altissima (Tall Ironweed), Vernonia baldwinii (Western Ironweed) and Vernonia noveboracensis (New York Ironweed) which can make plant ID difficult in the field. Expect to wait 3 years for it to flower.
