In xeric limestone prairies (XLPs, also known as “glades”), soil depth and fire are commonly posited to affect plant community composition and structure. Through mediating plant competition, these factors may explain plant distribution in XLPs, including mechanisms driving edaphic endemism. In a XLP in southwest Missouri, the abundance of Lesquerella filiformis Rollins (Missouri bladderpod), a rare winter annual, was higher in open sites, where competition was presumably low, than in Juniperus virginiana L. (eastern redcedar) or hardwood canopy cover types; L. filiformis density in the latter two cover types varied among years. Open, J. virginiana, and hardwood canopy cover types were distributed along an increasing soil depth gradient. During flowering of L. filiformis in April, photosynthetically active radiation was highest in open sites, intermediate below hardwood canopy (prior to leaf-out), and lowest below J. virginiana canopy. Removing J. virginiana was associated with greater increases in L. filiformis abundance between 2003 and 2005, and the basal area removed was positively associated with the magnitude of increase in plant abundance. These findings supported the hypothesis that interspecific competition, presumably at least partly for light, limited the distribution of L. filiformis in XLPs. While higher plant densities indicated that L. filiformis preferred open microhabitats, thinning J. virginiana provided a management option that increased L. filiformis density in marginal habitats subject to woody plant encroachment. Because factors affecting L. filiformis germination, establishment, growth, and survival likely vary along relatively fine-scale environmental gradients, (micro-) habitat specific management of XLP vegetation may assist in protecting rare edaphic endemic plant species, such as L. filiformis.