Throughout the United States, flowering occurs from late June to early September. Furthermore, the plant's fuels are concentrated on aboveground erect stems, so there is little fuel at the soil surface to promote soil heating. It is doubtful that marsh fires could destroy all of the purple loosestrife seeds stored in the soil. Seedling establishment following fire is probable. Most purple loosestrife plants sprout from the caudex following fire.
Fire is an ineffective method of purple loosestrife control because few plants are killed.
Purple loosestrife control in Voyageurs National Park. A Resource Management Bulletin. Distribution of mammals, reptiles, and amphibians by BLM physiographic regions and A.W. Kuchler's associations for the eleven western states. U.S. Department of the Interior, Bureau of Land Management. Eyre, F. H., ed.