Vernonia lettermanii 'Iron Butterfly'

Common Name: ironweed 
Type: Herbaceous perennial
Family: Asteraceae
Zone: 4 to 9
Height: 2.00 to 3.00 feet
Spread: 2.00 to 3.00 feet
Bloom Time: July to August
Bloom Description: Purple
Sun: Full sun
Water: Dry to medium
Maintenance: Low
Flower: Showy
Attracts: Hummingbirds, Butterflies
Tolerate: Drought, Erosion, Dry Soil, Shallow-Rocky Soil


Easily grown in medium to dry, well-draining soils of average fertility in full sun. Tolerant of various soil conditions, including hot, dry, rocky, and alkaline. Also tolerant of occasional flooding and drought once established. Hardy in Zones 4-9.

Noteworthy Characteristics

Vernonia lettermanii, commonly called ironweed or Letterman's ironweed, is an upright, clump-forming, herbaceous perennial native to rocky outcrops, floodplains, and river scours in west-central Arkansas and adjacent areas of Oklahoma. Plants can reach around 2' tall with an equal spread. The finely textured leaves are thin and narrow (up to 3" long and around ⅛" wide). Terminal corymbs (branched, flat-topped inflorescences) of bright purple flowers appear in mid to late summer. Highly attractive to hummingbirds, butterflies, and other pollinators. Synonymous with V. lettermannii.

Genus name honors William Vernon (d. c. 1711), English botanist who collected in Maryland in 1698.

The specific epithet lettermanii honors George W. Letterman (1840-1913), an American botanist and educator who collected extensively in Missouri, particularly along the Meramec River.

'Iron Butterfly' is a vigorous ironweed cultivar selected for its compact, densely mounding habit and showy, long-lasting display of purple blooms.


No major pest or disease problems. Stems can bend and arch, particularly if the soil is too rich or if full sun conditions are not provided.


A rugged perennial that can provide a fine texture to pollinator gardens, native planting, slopes, rock gardens, and xeriscapes. Mass plantings create a spectacular late-season display. Pairs well with the bright yellow blooms of goldenrods (genus Solidago).