California Maidenhair Fern :

Adiantum jordanii
NATIVE

Description (Jepson, PlantID.net)

Fern (Polypodiopsida)
- Ferns are a early group of vascular plants that produce spores (reproductive cells)
  - Produce no flowers or seeds
  - Fossil records date back almost 400 million years, versus 130 million years for flowering plants
Brake Family (Pteridaceae)
Perennial herb
- Grows from short creeping rhizomes (horizontal underground stems)
Fronds
- Compound (divided into leaflets), with 2-3 levels of division (2-3 pinnate)
- Leaflets are round or fan-shaped, slightly lobed, and finely-toothed
- Stalks (petioles) are dark brown to black, smooth, and wiry
Sori
- Sori (singular: sorus) are clusters of spore-producing, sac-like structures called sporangia (singular: sporangium)
  - Sporangia sacs split open to catapult mature, microscopic spores, which are wind dispersed
- Located in the curled-under margins of the leaflets
- Have no indusium (plural: indusia), a tissue flap sometimes covering sori

Distribution

Native to California
- Grows in soil and rock crevices on shaded hillsides and in moist woodlands
- See Calflora for observations of this plant
Outside California, grows from Oregon to Baja California, Mexico
Grows at elevations to 3,775 ft.

Uses (San Mateo County Parks prohibits removal of any natural material)

Native people
- Decoction of the plant used for internal pain, purifying blood, and expelling afterbirth (California Ohlone)
- Stems used to keep pierced ears from closing or as ear decoration (California Pomo)
- Roots used for binding baskets and stems for basket designs

Name Derivation

Adiantum (ad-ee-AN-tum) – from the Greek for “unwettable,” referring to the fronds shedding water
jordanii (JOR-dun-ee-eye) – a tribute to Rudolf Jordan, Sr. (1818-1901), a German immigrant to California, who collected this fern and had it identified by German botanist Karl Mueller, who named the species after Jordan
Maidenhair – implies fine hairs, which may refer to the slender stems or the many fine roots

Notes

Watch this short video showing fern reproduction in action (KQED 2024)
New fronds grow at the beginning of the wet season and dry up in late fall
Host to the fungus-like microorganism Phytophthora ramorum, which causes Sudden Oak Death (SOD)
- At Edgewood, the 2 species known to be highly susceptible to SOD are coast live oak (Quercus agrifolia var. agrifolia) and Pacific madrone saplings (Arbutus menziesii)
- For a complete list of known hosts and host associates see USDA Risk Analysis for Phytophthora ramorum, pp.6-9

ID Tips

To distinguish from other Edgewood ferns, look for fan-shaped, delicate leaflets

At Edgewood

Found in woodlands on moist, shaded hillsides and stream banks
- See iNaturalist for observations of this plant

Specific References

American Fern Society. About Ferns. Resources.

Anthropology Museum, California State University, Sacramento. Enduring Traditions: Baskets in Native California, a Mobile Classroom Outreach Trunk.

California Department of Parks and Recreation. 2019. California Indian baskets.

KQED San Francisco. 2024, April 16. Watch ferns get freaky [Video]. Deep Look. YouTube.

U.S. Forest Service. What are ferns? Forest Service. United States Department of Agriculture.

General References

Calflora Database. 2014. Berkeley, California.

Calscape. 2018. California Native Plant Society.

Corelli, T. 2004. Flowering Plants of Edgewood Natural Preserve (2nd. ed.). Monocot Press, Half Moon Bay, California.

Elpel, T.J. 2013. Botany in a Day: The Patterns Method of Plant Identification. HOPS Press, Pony, Montana.

Harris, J.G., and M.W. Harris. 2013. Plant Identification Terminology: An Illustrated Glossary. Spring Lake Publishing, Spring Lake, Utah.

Keator, G. 2009. California Plant Families. University of California Press, Berkeley and Los Angeles, California.

Regents of the University of California. Jepson eFlora. Jepson Herbarium. University of California, Berkeley.