The conservation of peripheral plant populations is paradoxical. Populations occurring on the edge of a species' range tend to be smaller, more isolated, and more genetically and ecologically divergent than central populations. The combination of these characteristics can impart novel evolutionary potential and local ecological significance, thus heightening their conservation value, while also making them less viable and more prone to local extinction. Public policy supports the conservation of peripheral populations, despite the commonness of the species elsewhere. However, the conservation of significant peripheral populations of nonlisted plants has been arbitrary and ineffective. The absence of explicit criteria to determine the conservation value of peripheral plant populations, the lack of finer-scale data on plant distributions, and a general unawareness of their value have hindered efforts to conserve them. We review the conservation value of peripheral plant populations and, using California as an example, describe regulatory methods to improve their conservation. We also propose a scheme to assess a population's conservation value.