The ability to propagate and successfully reintroduce rare plant species is an important component in the conservation biologist's toolbox. Unfortunately for many species, propagation methods and details about the species' life histories, which can potentially inform reintroduction efforts, are often unknown. We describe for the first time the pseudoannual life cycle of rough-leaved loosestrife (Lysimachia asperulifolia Poiret [Primulaceae]) and techniques that we have used to vegetatively propagate and reintroduce this federally endangered species endemic to the Atlantic Coastal Plain of the United States. Using simulated dormancy and controlled soil temperatures, we increased the number of collected viable rhizomes by approximately 76% over one growing season. At two translocation sites, stem numbers increased an average of 318 ± 145 SD % in five of seven test plots between 2004 and 2010. Using dormant-season–harvested rhizomes and/or reducing competition prior to transplanting via mowing or using herbicides greatly improved translocation success. Only plots receiving neither competition-reduction treatment and outplanted with summer harvested rhizomes showed reductions (73 ± 21 SD %) in the number of stems. Although limited flowering and no capsule production was detected at the translocation sites, a similar lack of sexual reproduction is common in many natural populations of L. asperulifolia. Overall, our results will allow the United States Fish and Wildlife Service and their conservation partners to more confidently pursue recovery goals for the species.