Although first collected in 1894, Adiantum shastense wasn’t described as a distinct species until 2015. It is native to the “mesic forests of the Eastern Klamath Range, close to Shasta Lake, on limestone and metasedimentary substrates”, where a number of locally-endemic species have been recognized in the past few decades.
As explained in Adiantum shastense, a new species of maidenhair fern from California (in PhytoKeys, 53(73-81)),
This region is host to a number of endemic plants and animals, most likely because of its unique geology, age and climate. These include the Shasta salamander (Hydromantes shastae); the Shasta monkey flower, (Erythranthe taylori); Shasta snow wreath, (Neviusia cliftonii); and the Shasta eupatory, (Ageratina shastensis). Of these species, the Shasta maidenhair fern has one of the widest geographic ranges, perhaps due to its wind-borne spores.
One of the distinguishing features of Adiantum shastense compared to the similar-looking Adiantum jordanii is the persistence of its fronds:
Green laminae are persistent throughout the summer, and the fronds appear to overwinter without dying back, perhaps until more than a year’s persistence. After the fronds die back, they ring the base of the plant, surrounding the new growth.
Many additional photographs of Adiantum shastense are available via CalPhotos: Adiantum shastense. The Jepson eFlora also has an account of the species and an identification key to Adiantum in California.
Martin Lenz, one of the collectors of the type specimen (pictured here — Martin, not the type specimen), helped us locate this population of Shasta maidenhair fern during last year’s collecting trip. Although other regional endemics were on our desired list, access was impossible due to unrepaired springtime road washouts and fires.