About Physematium oreganum (D.C.Eaton) Trevis.
Physematium oreganum, also known by its scientific name Physematium oreganum (D.C.Eaton) Trevis., produces fronds (leaves) that are twice pinnate to pinnate-pinnatifid, meaning the second division of the leaf does not extend fully to the base. These fronds grow from a short, scaly rhizome. Individual plants sometimes grow as a single clump, but can form an elongated mass when the rhizome is longer. Mature fronds reach up to 25 cm in length and 12 cm in width, and are held in an upright to angled position. The rachis (leaf stem) may have sparse, very short glandular hairs, and the species can be distinguished from the similar Physematium scopulinum by its lack of long rachis hairs. Small round sori grow on the underside of pinnae, and are initially partly covered by a narrowly lobed indusium. Physematium oreganum most commonly grows in open rocky areas and on rock outcrops. It has a wide distribution across the western United States and southwestern Canada, and occurs in more scattered locations further east.
