California Maidenhair

Adiantum jordanii occasionally hybridizes with A . aleuticum where their ranges overlap in northern California, yielding the sterile hybrid Adiantum × tracyi C. C. Hall ex W. H. Wagner. Adiantum × tracyi , morphologically intermediate between its parental species, can be distinguished from A . jordanii by its broadly deltate leaf blade that tapers abruptly from the 4(--5)-pinnate base to a 1-pinnate apex. It is best separated from A . aleuticum by leaf blades with a strong rachis, and by ultimate blade segments that are less than twice as long as broad. Adiantum × tracyi shows 59 univalents at metaphase; its spores are irregular and misshapen (W. H. Wagner Jr. 1962).

Stems short-creeping; scales reddish brown, concolored, margins entire. Leaves arching or pendent, clustered, 30--45 cm. Petiole 1--1.5 mm diam., glabrous, not glaucous. Blade lanceolate, pinnate, 20--24 × 8--10 cm, gradually reduced distally, glabrous; proximal pinnae 3(--4)-pinnate; rachis straight, glabrous, not glaucous. Segment stalks 1--4 mm, with dark color ending abruptly at segment base. Ultimate segments fan-shaped, not quite as long as broad; base truncate or broadly cuneate; margins of fertile segments unlobed but very narrowly incised, sterile segments with margins lobed, denticulate; apex rounded. Indusia transversely oblong, 3--10 mm, glabrous. Spores mostly 40--50 µm diam. 2 n = 60 .

Calif., Oreg.; Mexico in Baja California.

Sporulating early spring--midsummer. Seasonally moist, shaded, rocky banks, canyons, and ravines; 0--1000m.

Treatment of the species in the Flora of North America.

Adiantum jordanii is a perennial species of maidenhair fern, in the Vittarioideae subfamily of the Pteridaceae. The species is known by the common name California maidenhair.

It is native to California and Baja California. A. jordanii is found in the southernmost part of its range in Baja California with such flora associates as Mimulus aridus and Daucus pusillus.

Each trailing leaf may reach over half a meter in length and is made up of many rounded green segments. Each segment has two to four lobes and it may split between the lobes, the underside of each segment bearing one to four sori.

Adiantum jordanii is a carrier of the fungus-like oomycete, Phytophthora ramorum, which causes Sudden Oak Death. The USDA enforces an import control, focusing intensely on areas (CA, OR, NY in U.S.) that are infected with Sudden Oak death. When sold, they must be identified by place of origin and must also be accompanied by a phytosanitary certificate. The USDA warns to not take cuttings from wild specimens.

Adiantum jordanii, from native plant nurseries, is used in native plant and wildlife gardens.