Vernonia missurica aka Missouri Ironweed

Vernonia missurica is also known as Missouri ironweed. It belongs to the aster family and grows each year. Its home is central and eastern North America. Its range runs south from southern Ontario, Michigan, and Nebraska. It reaches as far south as Alabama and Texas. Wild plants grow by streams and in wooded swamps. They also grow in damp meadows, prairies, and fields. They grow on disturbed ground, too. In Missouri, they grow across much of the state.

Plants form upright clumps with stiff stems full of leaves. Most garden plants reach 3–5 feet (0.91–1.52 metres) tall. Some reach 6 feet (1.83 metres). In gardens, clumps tend to spread about 4 feet (1.22 metres). Chicago trials found plants about 5 feet (1.52 metres) wide. Fine hairs coat the stems, which branch near the top. The narrow leaves have toothed edges and hairs beneath. Each leaf can reach about 7 inches long. Leaf shapes range from a lance to a narrow oval.

Purple blooms add color late in the growing season. Chicago lists the bloom time as July through August. Its profile also says late summer through mid-fall. The blooms span about one inch. Each head tends to have more disk florets than other ironweeds. These are the small flowers that make up the head. Hairs on stems and leaf undersides help tell this species apart. Plants draw birds and butterflies, bringing wildlife to borders. They can cross with other native ironweeds. This can make them hard to tell apart.

Grow Missouri ironweed in full sun, with a moderate water supply. It suits both average garden soil and wetter ground. Wild plants favor damp sites and can bear brief floods. Plants tend to grow taller in moist soil. Chicago lists USDA hardiness zones 4–9 for this plant. Missouri Botanical Garden says it is easy to grow. It also says the plant needs little care. Seeds offer a simple way to grow new plants.

Use it behind shorter plants in a mixed border. It suits cottage gardens and gardens of native plants. It fits prairie plantings, too. Its height can form a screen for part of the year. Cut stems back in late spring to keep plants shorter. To curb new seedlings, cut off old heads before seeds form. It resists deer, which helps where deer feed on garden plants. Missouri Botanical Garden reports no major pest or disease concerns.