Geum macrophyllum ssp. perincisum is a tall herbaceous plant in the rose family (Rosaceae) with large divided leaves and yellow flowers that develop into nettle-like heads. This species grows in the boreal zone in meadows, lakeshores and riverbanks. Plants grow up to 70 cm tall from a stout rhizome. G. macrophyllum ssp. perincisum has both basal and stem leaves. The basal leaves are lyrate-pinnate with serrate margins, the large apical lobes are deeply cleft, and the other opposite pinnae much smaller. The few stem leaves are trifoliate and serrate. At the top of the tall stem the plants branch and produce a few small, perfect, and radially-symmetrical flowers. The flowers have five small, ovate petals, 7 mm long, widely spaced. The fruiting head is round, holding several achenes (fruits) with hooked styles, each achene 7-10 mm long. This subspecies differs from ssp. macrophyllum by the division of the leaves (more deeply cleft than ssp. macrophyllum) and its biogeography. This species is distinguished from other local species of Geum by the leaf shape—G. rossii and G. glaciale have evenly pinnate leaves and are tufted plants that grow in the alpine zone.
Largeleaf avens is a perennial species that flowers mid-summer in Denali.
The pollination biology and mating system of this species has not been studied. Flowers are bisexual (plants monoecious) and likely insect-pollinated. The hooked beaks of the achenes serve as burrs, catching on fur, feathers or clothing and transporting seeds with the movement of animals.
Largeleaf avens is a boreal-montane North American species that occurs across Canada, the northern tier of U.S. states and the western Cordillera of the United states, including Alaska. In Alaska, this species occurs from isolated localities on the North Slope to the interior, where it occurs occasionally, to Kodiak Island and the northern southeast panhandle at its southern extent. In Denali, the species occurs sporadically on both sides of the Alaska Range.