Seedlings can mature and flower within 8-10 weeks. Seeds lack a dormancy period. Seeds stored in dry soil at room temperature can survive for at least 14 years, but longevity under field conditions is unknown. Most seeds germinate in spring when conditions become favorable. Fall-germinated seedlings may overwinter under mild conditions.
Seedlings typically emerge after water levels subside.
Monitoring uninfested areas and hand-pulling newly discovered seedlings before seed is produced can help prevent the spread of purple loosestrife . Cutting flowering stems followed by flooding can help control but not eliminate dense infestations. Cut stems can re-root under certain conditions. Plants are most susceptible to systemic herbicide effects during the late flowering stage. Unlike hyssop loosestrife , threebract loosestrife has triangular calyx tube appendages that resemble the sepal lobes and are covered with red glands.