We are significantly behind in our rainfall totals for this year, but during the last week the rains have made a valiant effort to catch up before Spring arrives.
This winter’s paucity of rainfall has impacted a number of our native plants, especially our deciduous fern species, including the Goldback Fern.
Pentagramma triangularis (syn. Pityrogramma triangularis) is a member of the Brake family of ferns (Pteridaceae), and related to our native California Maidenhair Ferns (Adiantum jordanii) that also grow on the farm.
Penta, meaning five, and gramma meaning lined, this species is named for its five-lobed, broadly triangular fronds.
The common name of Goldback, or Goldenback Fern, is an accurate descriptor of this species, because when a mature leaf is turned over, golden yellow waxy spores are visible on the underside of the fern’s fronds.
Native to the western United States, this species can be found growing from British Columbia, south throughout California, and east to Nevada and Idaho, growing below 7,500 feet in elevation.
This species favors dry brushy areas, and rocky slopes, and is frequently found growing in the understory of oak and mixed evergreen forests on rocky outcroppings and road cuts.
However, Goldback Fern’s diminutive size makes this particular species very easy to overlook.
This is the smallest species of fern that is known to grow on the farm. During the winter months we find it growing on some of the steepest banks above the road, mixed in with various grasses.
In the summer months however, without water, this fern becomes dormant, and seems to all but disappear.
Despite its preference for rocky exposed areas, Goldback Fern also tolerates significant shade, and occasionally we find it tucked in between the native redwood sorrel leaves, beneath the oaks. It rarely seems to thrive there, however.
We primarily find this fern growing beneath Live Oaks, and California Bay Laurels, but not under our Coast Redwoods. The Goldback Fern seems to resent the rich acidic layer of redwood litter that accumulates at the base of those trees.
Goldback Fern has an open growth habit, with fronds arranged in clusters on brown-black stems, up to 12 inches in length.
Not every Goldback frond has a golden yellow ventral surface. Before the appearance of the yellow spores, whitish colored sori may be visible along the margins of the black veins.
The fronds of the Goldback Fern grow much like other fern species, first appearing as small fiddle-heads.
Gradually, the frond begins to unfurl.
Until the pinnae are fully extended, the fronds have a somewhat contorted appearance.
Frond size can vary tremendously depending upon the stage, and location, of growth. Newly emerging fronds in exposed sites are very small, and can be easy to miss.
Frond size seems limited by the degree of the exposure. In our loose soils, that dry quickly once the rains cease, mature fronds don’t grow much larger than this.
In more protected locations, in areas of shade, fronds may be significantly larger.
The frond edges may be curled under, especially during periods of water stress.
Where the plants are more protected the pinnae have a broader appearance.
Presumably, the curling of the edges of the pinnae serves to decrease surface area across the frond, and reduce water loss during warmer, and drier weather.
New fronds also appear to be more narrow than those that are more mature, so there can be much variation in frond appearance, even on the same plant.
Like the Western Sword Fern, Native American peoples found the Goldback Fern to have medicinal qualities. The Karok used Goldback Fern as an analgesic, and to control pain after childbirth, and the Miwok chewed the fern as a remedy for toothache. Yurok children would apparently use the Goldback Fern fronds as decoration, pressing the spore side against their skin, leaving behind a decorative golden impression.
We’re fortunate to have so many Goldback Ferns that freely volunteer to grow here. This species reportedly grows in USDA zones 6a through 9b, but is not readily obtainable from most plant nurseries. However, some area speciality native plant nurseries may occasionally stock them, and if you have them growing in your gardens already, they can be propagated through division from late winter to early spring.
 Daniel E. Moerman’s Native American Ethnobotanical Database