Asplenium ruta-muraria, commonly known as Wall-rue, is a small, evergreen epipetric fern that thrives on limestone and other calcareous substrates. It is native to a variety of habitats including rocky slopes, cliffs, and walls, particularly where limestone is present, across Europe, East Asia, and eastern North America. Wall-rue typically grows to about 5 inches (13 centimeters) in length.