Missouri Ironweed is a tall, upright native perennial with sturdy stems and clusters of vivid purple flowers that appear from late summer into early fall. It is best planted toward the back of a border or in a meadow where its height can be appreciated. It prefers consistent moisture but is adaptable once established. Give it plenty of room to develop. Cutting the stems back by about one-third in early summer can encourage a shorter, sturdier plant and reduce flopping. You can divide established clumps in spring if they become too large.