Leather Fern (Polypodium scouleri). California Polypody fronds turn brown and die back by summer whereas Leather Fern is evergreen. Both ferns have fronds with an oblong-ovate shape but the tip of a Leather Fern frond is elongated. The sori of the California Polypody are typically bright yellow, becoming brown when the plant begins to die back whereas Leather Fern sori develop into a dark orange color. California Polypody is very abundant in the park, while Leather Fern is rare, with only one small patch reported to date. California Polypody is also similar to Acrid Fern (Polypodium calirhiza) but they are difficult to tell apart visually.