Calcicole

thumb|right|Common rock-rose forming low mats on shell limestone and sandy soil of the Saupurzel, a limestone hill in [[Bavaria]] Calcicoles—literally "lime‑dwellers"—are organisms, most commonly vascular plants but also including bryophytes, lichens and other taxa, that grow preferentially on calcium-rich, often alkaline, substrates. Because they grow only on specific lime-rich soils, calcicoles give ecologists a clear, real-world example of how soil chemistry determines where organisms can live. Their distribution on chalk, limestone and other calcareous rocks reflects a suite of physiological adaptations that enable them to regulate cytosolic Ca2+, acquire otherwise insoluble iron and phosphorus, and withstand high soil pH. In contrast, calcifuges ("lime‑avoiders") dominate on acidic, aluminium‑rich soils. Modern research has linked the calcicole habit to indicators such as Heinz Ellenberg's soil‑reaction values and the Index of calcifugy, while pharmacognostic studies have uncovered an array of bioactive compounds in many limestone specialists.

==Terminology and historical use==