Distinguishing Parsley Ferns (Cryptogramma spp.)

Parsley ferns (Cryptogramma spp.) are relatively small rock-loving ferns, which are sometimes known as rock-brakes. Unlike our other rock ferns, spore-bearing structures are on separate fertile fronds that are usually taller than the sterile fronds. There are two species of parsley ferns in the Cascades. American parsley fern (C. acrostichoides) is common throughout the Western Cascades and is found elsewhere in western Oregon. It is found primarily at low to middle elevations. Cascade parsley fern (C. cascadensis) is found only at higher elevations, mostly in the High Cascades. Both species have also been seen in the Wallowas. The third species in Oregon, Steller’s rock-brake (C. stelleri), is a rare inhabitant of the Wallowas, although its range stretches across much of the northern US.

Left: Cascade parsley fern in the Calapooyas; Right: American parsley fern at Table Rock Wilderness

Left: Cascade parsley fern in the Calapooyas; Right: American parsley fern at Table Rock Wilderness

For a number of years, I’ve been uncertain of my identification of Cascade parsley fern. Recently (see More Discoveries along the Calapooya Crest), I got a great lesson in distinguishing our two Cascade species from the expert, Ed Alverson, who first described Cascade parsley fern in 1989 (see Cryptogramma cascadensis, a New Parsley-Fern from Western North America,” in the American Fern Journal, Volume 79 Number 3, pp. 95–102). In addition to genetic differences, there are several morphological characteristics that can help separate the two species in the field.

American Parsley Fern (Cryptogramma acrostichoides)

Sterile fronds are evergreen and thick. Dead fronds from the previous year are often visible at the base of the plant, having survived the winter but not dying until the new year’s fronds are formed.

Sterile fronds are noticeably lighter green on the back than on the front.

Hydathodes (according to Wikipedia: a modified pore, especially on a leaf, that exudes drops of water) form depressions in the thick leaves.

The rachis has small hairs in the groove.

Cascade Parsley Fern (Cryptogramma cascadensis)

Sterile fronds are deciduous and thin. There is rarely any evidence of the previous year’s fronds, which die long before the new year’s fronds emerge.

Sterile frond color is the same on the back as on the front.

Hydathodes are flush with the leaves and are narrower.

The rachis has no hairs in the groove.

Left: Cryptogramma cascadensis; Right: Cryptogramma acrostichoides

Left: Cascade parsley fern; Right: American parsley fern. You can see the lighter color on the underside of the frond in American parsley fern. While the teeth and lobes look smaller on Cascade parsley fern in this scan, apparently there are wide variations in leaf shape in both species, so this may not be a useful diagnostic.

 

The hydathodes are are the different areas of tissue out near the ends of the veins. Left: Cascade parsley fern has small hydathodes that show up as lighter areas. They are best seen by looking at the fronds against the light; Right: American parsley fern has larger hydathodes. Its leaves are thicker, and the hydathodes aren't as thick, so they form a small depression.

The hydathodes are the areas of different tissue out near the ends of the veins. Left: Cascade parsley fern has small hydathodes that show up as narrow lighter areas. They are best seen by looking at the fronds against the light; Right: American parsley fern has larger hydathodes. Its leaves are thicker but the hydathodes aren’t as thick, so they form a small depression.

 

Left: Cascade parsley fern rachis without hairs; Right: American parsley fern rachis with hairs inside the groove

Left: Cascade parsley fern rachis without hairs; Right: American parsley fern rachis with hairs inside the groove

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