HIKES AND NATURE WALKS IN THE SAN GABRIELS
Walks on the Wild Side, Fall-Winter, 2008-9
February 4, 2009
West Fork in Winter
2. Ferns and Rocks
Ferns are intimately associated with different types of rocky places in the San Gabriel Mountains. All photos by Graham.
These three ferns are found in sunny, rocky places: coffee, bird's foot and gold back. These pictures were taken in the parking lot above the West Fork bridge on Hwy 39. The slope faces southeast.
Coffee fern, Pellaea andromedifolia. The leaves are green when new, then turn red, purplish, or brown.
Bird's foot fern, Pellaea mucronata ssp. mucronata.
Gold back fern, Pentagramma triangularis ssp. triangularis. See the gold back on the new young shoots still rolled up in balls. This particular photo was taken at the first stop, but gold back is found in the parking lot as well.
California polypody is found growing on top of mosses on top of rocks in sun or shade. It is deciduous and not seen the rest of the year.
California polypody, Polypodium californicum. Polypody growing in sun on slope above parking lot.
California polypody, Polypodium californicum. Polypody on north-facing rock wall under oaks in shade.
Coastal wood fern is found locally only under oaks on top of rocky ridges.
Coastal wood fern, Dryopteris arguta. Single large plant under oak.
Coastal wood fern, Dryopteris arguta. Growing next to oak root on the rocks in dry shade, the ferns behind it are polypody.
Southern maidenhair fern grows where there is water, rock walls like waterfalls and, locally, limestone or calcium from precipitates, seeps or concrete structures like dams.
Southern maidenhair fern, Adiantum capillus-veneris.
Southern maidenhair fern, Adiantum capillus-veneris. On weeping wall along West Fork Road. The vines are California blackberry.
There are two species of maidenhair ferns in our area, Adiantum capillus-veneris, southern maidenhair, and A. jordanii, California maidenhair, that are easy to confuse.
leaf segments cut or lobed often > 1/4 way to base, margins at base converging at 45–90° = Adiantum capillus-veneris
leaf segments cut or lobed often < 1/4 way to base, margins at base converging at 90–180°, rarely to 240° = Adiantum jordanii
This is difficult to use in the field because you have to make judgement calls without using measuring instruments.
Often you have a base greater than a right angle with cuts greater than 1/4. What's a body to do? Use the Flora of North America discriminant, that's what:
dark color of stalks extending into base of ultimate segments = Adiantum capillus-veneris
dark color of stalks ending ± abruptly at base of ultimate segments = other species
It works best in the field, you have to look closely in the photos. Here is a photo by Michael from his recent trip to Zuma Canyon. Most of the angles at the bases are greater than 90 degrees, but you can see the black extending into or along the blade which distinguishes it as Adiantum capillus-veneris.