Hydrophyllum brownei is a rare endemic species restricted to the Ouachita Mountains of Arkansas. One objective of this study was to model H. brownei population density by investigating the influence of sun exposure, soil characteristics and crowding. The most parsimonious model including shade alone best predicted population density, in which increasing shade was correlated with greater population densities. Reproductive capacity of different parts of the root was tested and individuals of the species were found to produce vegetative shoots from all portions of the root. This indicates that individuals are prolific vegetative reproducers, especially in circumstances of intense physical soil disturbance that break apart root systems. Leaf number was strongly correlated with number of root swellings and was determined to be a good predictor of individual plant stage. It was found that populations were structured either “normally,” with about equal numbers of individuals in all stage classes, or “dynamically,” skewed to a greater number of early stage individuals. Levels of shade relate to population density and site disturbances likely influence the density and stage structure of populations due to the life history trait of extensive vegetative reproduction from the roots. Further questions about genetic diversity and the ability to colonize new sites should be investigated to gain a better understanding of limits to H. brownei's distribution.