Peltigera rufescens, commonly known as the field dog lichen or field pelt, is a species of terricolous (ground-dwelling), foliose lichen in the family Peltigeraceae. This common and widespread species has a cosmopolitan distribution, often found in dry, sunny habitats on basic soils, limestone, and nutrient-rich silicate substrates. The lichen forms rosettes up to 20 cm (8 in) in diameter, with a grey to brown thallus densely covered with a soft, velvety tomentum. Its lobes, typically 3–5 cm (1.2–2.0 in) long and 5–10 mm (0.2–0.4 in) wide, have distinctively curled upward edges. The underside of the thallus features a network of veins and rhizines, which anchor the lichen to its substrate. P. rufescens reproduces both sexually through apothecia (fruiting bodies) and asexually via regeneration lobes. It forms a symbiotic relationship with cyanobacteria from the genus Nostoc as its photobiont. The species is notable for its ability to bioaccumulate heavy metals and its adaptive responses to ultraviolet-B radiation, making it a subject for ecological and physiological studies.

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