Serpentine is California's state rock. Composed of hydrous magnesium iron phyllosilicate, it is typically a dark greenish-gray color, often splotchy or veined, with a waxy texture. It is a relatively soft rock (hardness 2.5 to 4) and a relatively light one (specific gravity 2.2 to 2.9). It has often been used for jewelry, stone carvings, railway ballasts, building materials, and road surfaces. Some serpentine rocks contain asbestos, which has sometimes been used as thermal insulation but can cause health problems if the rock breaks down into tiny particles that are inhaled. Naturally occurring asbestos, when left in the ground undisturbed, is not generally believed to pose a significant health threat.
Serpentine is formed when parts of the ocean floor are pushed to the surface of the land, which has happened in the Smartville ophiolite. Named after the town of Smartsville in Yuba County, this ophiolite passes through much of the northern California foothills, reaching from northwestern Lake Oroville southeast to Cameron Park. In Yuba County, it passes through Browns Valley, Brownsville, Challenge, Dobbins, Frenchtown, Greenville, Loma Rica, Oregon House, Rackerby, the Spenceville State Wildlife Area, and of course the town of Smartsville.
All soil consists largely of broken-down rock, so soil in areas of serpentine rock consists largely of broken-down serpentine rock. Because of the unusual chemical components of serpentine rock, soil in these areas is toxic to many plants. Specifically, soil in the Smartville ophiolite contains high levels of nickel, chromium, and cobalt, low levels of potassium and phosphorus, and a low ratio of calcium to magnesium. As a result, the plants that survive in these areas tend to be native species—often rare and endengered species—that have evolved here over millennia. Areas of serpentine-derived soil can be identified by the fact that they are strips of open shrubland with a few scattered small trees, even when adjacent non-serpentine areas are densely forested. In Yuba County, serpentine-adapted plants can be seen especially in areas on Browns Valley Ridge in northwestern Browns Valley, just northeast of Flanly Hill in Oregon House, between Holman Hill and High Prairie south of Collins Lake, on Ure Mountain southeast of Collins Lake, in northern and eastern Rackerby, just north of Chitterden Ridge near Rackerby, just northwest of Ruff Hill in Brownsville, just south of Mount Hope near Challenge, and surrounding Pike County Peak near Greenville.
People who try to plant conventional garden plants in serpentine areas such as the Smartville ophiolite will be very frustrated, because most of their plants will die. However, there are advantages to gardening in serpentine areas: many weedy plants do not survive in these areas, and our native poison oak tends not to survive either. Gardeners who select appropriate species for serpentine areas can create extremely successful gardens. The following Yuba County native species are among those that grow successfully in areas of Smartville ophiolite.1
Trees
(See the Conifers, Oaks, and Native Edible Fruits pages for more information about some of these species.)
bigleaf maple california buckeye Pacific madrone sticky whiteleaf manzanita MacNab's cypress incense cedar (also called white cedar, post cedar, or bastard cedar) birchleaf mountain mahogany tanoak foothill pine (also called gray pine, pinon pine, or bull pine) bitter cherry canyon live oak (also called goldcup oak or maul oak) Leather oak* California black oak California bay laurel (also called Oregon myrtle)
*found exclusively on serpentine soils
Shrubs
(See the California Lilacs, Buckthorns, Monkeyflowers, and Roses pages for more information about some of these species.)
red-twig dogwood (also called red osier dogwood or American creek dogwood) bush poppy yerba santa California coffeeberry toyon (also called Christmas berry) cream bush sticky monkeyflower ninebark dwarf wood rose ground rose
Perennial Herbs
Monocots
Grasses and Grasslike Plants
(See the Ryegrasses, Oniongrasses, and Sedges pages for more information about some of these species.)
Stillman's needlegrass woodland brome (also called Chinook brome or narrowflower brome) Brainerd's sedge blue wildrye meadow barley California melic Geyer's oniongrass
Bulbs and Corms
Asparagus Family
(See the Cluster-Lilies page for more information about these and other cluster-lily species.)
California cluster-lily Sierra brodiaea Bridges' brodiaea
Lily Family
(See the Tulips and Fritillaries pages for more information about some of these species.)
fairy lantern (also called white globe lily) blue star tulip naked mariposa tulip Sierra fawnlily (also called adderstongue) checker lily chocolate lily Butte County fritillary scarlet fritillary fragrant fritillary panther lily
Onion Family
(See the Onions page for more information about these and other onion species.)
narrowleaf onion papery onion Sanborn's onion
Other Bulbs and Corms
clustered lady's slipper longtube iris (also called bowltube iris or ground iris) Hartweg's doll's lily
Dicots
Aster Family
(See the Daisies and Mule Ears pages for more information about some of these species.)
lesser California rayless fleabane California everlasting (also called California cudweed) hairy gumplant Bolander's mule ears
Carrot Family
Mother Lode yampah snakeroot (also called purple sanicle) Hartweg's umbrellawort
Mint Family
(See the Coyote Mints page for more information about some of these species.)
Shelton's coyote mint coyote mint Sonoma sage (also called creeping sage)
Other Families
(See the Milkweeds, Paintbrushes, Willowherbs, and Buttercups pages for more information about some of these species.)
Western columbine California spikenard (also called elk's clover) purple milkweed purplish morning glory Frosted paintbrush padre's shooting star California fuchsia sun rose seep monkeyflower (also called common yellow monkeyflower) largeleaf sandwort Sierra milkwort whitevein wintergreen (also called whitevein shinleaf) California buttercup (also called common buttercup) checker mallow
Ferns
(See the Horsetails and Maidenhair Ferns pages for more information about these and other fern and horsetail species.)
five-finger fern (also called Western maidenhair fern) scouringrush horsetail California polypody Western brackenfern
Annuals
Aster Family
(See the Tarweeds and Tidytips pages for more information about these and other tarweed and tidytip species.)
sticky Western rosinweed truncated Western rosinweed Colusa tidytips meager tarweed (also called small tarweed or little tarweed)
Other Families
(See the Bentgrasses, Willowherbs, Buckwheats, Monkeyflowers, and Clovers pages for more information about some of these species.)
littleleaf bentgrass miner's lettuce little chaparral willowherb wickerstem buckwheat Sierra bluecup brownies (also called purple mouse ears) California sandwort downy pincushionplant (also called purple pincushionplant) dotseed plantain (also called foothill plantain or California plantain) Sierra mock stonecrop valley checker mallow sour clover (also called bull clover) hairy maiden clover (also called smallhead field clover) tomcat clover
Footnotes
1. CalFlora.org