This is a large genus of over 150 species in North America, most of which are western, although a few are centered in the southeastern United States.

1. Stamens long-exserted (2-6 mm) beyond corolla, glabrous.

P. tanacetifolia

1. Stamens scarcely if at all longer than the corolla, the filaments hairy.

2. Corolla bell-shaped, with distinct tube, the lobes entire; range northern (Isle Royale).

P. franklinii

2. Corolla nearly rotate (flat), the lobes fringed; range southern.

P. purshii