Whorled lousewort is a pink-flowered herb found in floodplains, meadows and lush tundra in Denali, recognizable by the arrangement of the purple flowers in the axils of their whorled stem leaves. Plants produce one to several flowering stems from a taproot. Most of the leaves are basal. These leaves are pinnatifid with dentate margins, from long petioles. Stem leaves are similar, but with much reduced or absent petioles. The flowers are verticillate, or arranged around the stem in whorls, as are the stem leaves. The flowers are purple-magenta, with darker veins. As in other Pedicularis species, P. verticillata has bilaterally symmetric flowers with two petals, the upper hooded and without teeth, the lowering flaring into three wide lobes. The sepals are fused into a small tube, covered with hairs. Fruits are dry capsules, splitting open to release many seeds. Whorled lousewort is the only member of the genus with whorled leaves with axillary flowers.
Pedicularis verticillata flowers in mid-summer. It is a short-lived perennial according to .
Pedicularis verticillata is monoecious with bisexual flowers. The species is pollinated by bees. In a study in the Yukon territory, P. verticillata set 94% of its fruit when open-pollinated, higher than any other Pedicularis tested (Macior 1975). Whether it is self-compatible has not been tested, but flowers excluded from insect visits did not set seed. Like other members of the genus, whorled lousewort is hemi-parasitic, deriving some of its nutrients from other plants.
Flowers were picked and sucked for the sweet nectar by Alaska Natives on Nunivak Island (Griffin 2001).
Pedicularis verticillata is an arctic-alpine amphi-Beringian species, ranging through Alaska to western Yukon, northern B.C. and Northwest Territory, and then west through Eurasia, with disjunctions reaching to Europe and China. This species is widespread in Denali on both sides of the Alaska Range, predominately in the alpine zone of the northern side, with a few boreal localities, radiating from the mountains outwards along large river systems.
Whorled lousewort's grows as low as 472 meters, but this is predominantly an alpine species. Its average occurrence is at 1043 m and peak frequency is above 1100 m. It is found on all levels of incline, where the average is 14 degrees, most commonly found on south-facing slopes of 20-28 degrees.