Serpentine Rock Outcrops

A rock outcrop community.
This rock outcrop community is dominated by buckwheats (Eriogonum spp.) and sedums (Sedum spp.). Photo by Julie Nelson.

A streamside rock outcrop community.
Trees as well as herbs can make a toehold in this challenging habitat. Trees present in this image include Jeffrey pine (Pinus jeffreyi), Douglas fir (Pseudotsuga menziesii) and incense cedar (Calocedrus decurrens). Photo by Julie Nelson.

The ultramafics of the Klamath-Siskiyou bioregion are a place where the bones of the earth show. Vegetation does not blanket and soften the slopes of this landscape. Rocks are exposed everywhere, sometimes with a thin cover of shrubs or herbs, sometimes with trees emerging from crevices, and sometimes apparently barren at first glance.

The harsh conditions imposed on plants by the climate and the mineralogy of serpentine rocks slow soil development. The stunted vegetation creates so little organic matter. The Mediterranean climate of wet winters and dry summers means that the combination of warmth and moisture needed for decomposition of dead plant material is present for only a few weeks of the year.

Serpentine rock outcrops characterize all elevations of this landscape, from grasslands and savannahs at low elevations, to the glaciated serpentine rock summits of the eastern Trinity Alps and Eddys, and in the dramatic river canyons of the Rogue, Smith, upper Trinity, and South Fork Sacramento Rivers. Plants that live in these places are able to find the moisture and shelter they need by sending their roots deep into rock crevices. Sometimes surface water emerges to drip down the rocks, creating habitat for moisture-loving plants such as Cypripedium californicum (California lady’s slipper orchid), Adiantum aleuticum (five-finger fern) and Pinguicula macroceras (horned butterwort).

The beauty of the rocks is enhanced by the loveliness of the wildflowers that inhabit them, creating breathtaking natural rock gardens. Some of the rarest and most beautiful Klamath-Siskiyou serpentine endemic plants are rock outcrop inhabitants: Arabis macdonaldiana (Macdonald’s rockcress), Galium serpenticum ssp. scotticum (Scott Mountain bedstraw), and Sedum moranii (Rogue River stonecrop).

Cheilanthes gracillima
Serpentine habitats are not very hospitable for ferns in general but several have been able to find a niche and an ability to survive the rigors of the serpentine. This lace lip fern is growing out of a crack in the serpentine bedrock (Cheilanthes gracillima). Photo by Steve Matson.

Epilobium siskiyouense
Siskiyou willowherb (Epilobium siskiyouense) is a strict endemic of serpentine habitats, generally observed growing in cracks or seams where some soil and moisture is available for its growth. Photo by Norman Jensen.

Eriogonum siskiyouense
Although the rock outcrops can seem to be depauperate of wildflowers, coming upon the beautiful Siskiyou buckwheat (Eriogonum siskiyouense) in full flower is a real treat. The succulent leaves allow this plant to store water when it is available so it can survive this extremely xeric environment. Photo by Ken DeCamp.

Eriogonum alpinum
Trinity buckwheat (Eriogonum alpinum) is a strict endemic of serpentine habitats found at high elevations such as Mt. Eddy in the Trinity Alps. Photo by Julie Nelson.

Pinguicula vulgaris
Not all of the rock outcrop communities are xeric. Some rock outcrop communities are wet such as this seep where common butterwort (Pinguicula vulgaris) may be found. Photo by Julie Nelson.

Sedum obtusatum ssp. obtusatum
As with all the sedums found in the Klamath-Siskiyous, they have made their niche in xeric rock outcrop communities, such as the Sierra stonecrop (Sedum obtusatum ssp. obtusatum). Their succulent leaves are able to store water for use when moisture is not available. Photo by Steve Matson.

Photo Gallery

Adiantum aleuticum
Adiantum aleuticum. Photo by Julie Nelson.

Collomia tinctoria
Collomia tinctoria. Photo by Steve Matson.

Draba aureola
Draba aureola. Photo by John Game.

Epilobium rigidum
Epilobium rigidum. Photo by Norman Jensen, Photo·grafica botanii.

Eriogonum strictum var. greenei
Eriogonum strictum var. greenei. Photo by Julie Nelson.

Eriogonum umbellatum var. humistratum
Eriogonum umbellatum var. humistratum. Photo by Julie Kierstead Nelson.

Galium serpenticum ssp. scotticum
Galium serpenticum ssp. scotticum. Photo by Julie Nelson.

Holodiscus microphyllus
Holodiscus microphyllus, rock spiraea. Photo by Julie Nelson.

Lewisia leeana
Lewisia leeana. Photo by Br. Alfred Brousseau, College of St. Mary, California.

Parks Creek Summit on Mount Eddy
Parks Creek Summit on Mount Eddy. Photo by Julie Kierstead Nelson.

Sedum laxum ssp. flavidum
Sedum laxum ssp. flavidum. Photo by Julie Nelson.

Veronica copelandii
Veronica copelandii. Photo by Ken DeCamp.

Our thanks to CalPhotos and its many contributors for many of the pictures in this photo gallery.