Common ironweed is a tall, midsummer to early fall perennial with long, leafy stems topped by showy clusters of purple or fuschia flower heads. In full sun to partial shade conditions with adequate moisture, it can be planted in rain gardens, wildflower gardens, native gardens, meadows, prairies, and in the backgrounds of beds and borders. This species is native to the Chicago region according to Swink and Wilhelm’s Plants of the Chicago Region and current research.
Size and method of spreading:
Common ironweed grows to 2 to 4 feet tall and 1 ½ to 3 feet wide. It spreads by self-seeding.
Native geographic location and habitat: (include C-value if appropriate)
The native range of common ironweed includes the Central United States. C Value: 8.
Attracts birds or pollinators:
Common ironweed attracts bees, butterflies, and skippers.
The hairless leaves of common ironweed are up to 6 inches long and 1 ¾ inches wide (narrowly ovate, lanceolate, or linear). The edges of the leaves have small, sharp teeth (serrate margins) and there is a prominent midvein. The undersides of the leaves are often pitted (faveolate). They grow in an alternate arrangement.
Common ironweed produces dense clusters of purple- to fuschia-colored compound flower heads. The flower heads are composed of 15 to 30 disk flowers and are approximately three-quarters of an inch in diameter. Each of the tubular disk flowers are divided into five long, narrow, spreading lobes at the tip. Protruding from the center of each disk flower is a long structure that divides into two curled sections at the tip (divided style). Surrounding the bases of the flower heads are green to purplish-brown, flattened, leaflike appendages (bracts) that occur in scalelike layers and have rounded tips. The flower heads grow in corymb-like clusters.
The small, dry fruit (achenes) of common ironweed have rust-colored, hairlike bristles on the tip that helps to distribute the seeds via wind.
Deadheading the spent blooms of common ironweed can help to reduce self-seeding and encourage production of additional flowers. Stems can be cut back in the late spring to reduce plant height. Taller plants may require staking for support.
List of pests, diseases, and tolerances:
Common ironweed is not susceptible to major issues with diseases. Moth caterpillars are pests that will bore through the stems and roots of common ironweed. It is deer and rabbit resistant due to the bitter taste of the foliage. This species can withstand short periods of flooding.