Wave-splashed bedrock shoreline ledges are best developed on sandstone in the Apostle Islands of Lake Superior. Stunted trees of northern white-cedar (Thuja occidentalis), paper birch (Betula papyrifera), showy mountain-ash (Sorbus decora) and green alder (Alnus viridis) are often present in crevices. Common herbs are tickle grass (Agrostis hyemalis), fireweed (Epilobium angustifolium), and Canada goldenrod (Solidago canadensis), but the flora often includes unusual plants such as bird's-eye primrose (Primula mistassinica), brook lobelia (Lobelia kalmii), and three-toothed cinquefoil (Sibbaldiopsis tridentata).