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. However, under most circumstances California loosestrife is not considered a weed. Unlike purple loosestrife , California loosestrife has glabrous stems, petals mostly 4-8 mm long , and linear inflorescence bracts with acute or rounded tips .