The identification of plants and plant assemblages that are common to stream reaches that gain water and those that do not is an important key in the study of limestone hydrology. In the Ozark Mountains of Missouri, a rapid change from a stream-channel growth of abundant willows (Salix spp.), touch-me-nots (Impatiens capensis), and sedges such as Carex Frankii and Eleocharis spp. to an abundant growth of bluestars (Amsonia illustris) indicates a rapid increase in depth to water. Vegetative indicators of hydrologic conditions are most helpful when used in conjunction with other information, but they are independently useful in pinpointing areas of abrupt hydrologic changes.