A New Perspective on the Flora of Mt Diablo
by Kevin Hintsa
It has been over fifty years since the publication of Mary Bowerman’s The Flowering Plants and Ferns of Mount Diablo, California. Nearly half the scientific names used then are now obsolete. Also, an additional hundred species (more or less) have been since found to exist on Mt Diablo. This spring UC Berkeley’s Jepson Herbarium announced its intentions to produce a new revision of Bowerman’s Flora, under the leadership of Barbara Ertter. The following plant species are some of the new additions to Bowerman’s Flora.
Common California Aster (Aster Chilensis, Sunflower Family) grows on the southwestern portion of Mt Diablo and is uncommon here. This species has either white or purple blossoms and lance-shaped leaves. Some of the specimens seem to resemble a Southern California species of Aster and might merit further study. look for it in the autumn.
Narrow-leaved Mule Ears (Wyenthia Angustifolia, Sunflower Family) is fairly common in some locations on the mountain, especially along Wall Ridge and lower Pine Canyon. It resembles several other species of yellow sunflowers, but note the narrow leaves and the even-sized leaf bracts that are quite hairy. Also note that the stem is often reddish. This species was most likely overlooked previously.
Seaside Heliotrope (Heliotropium Curassavicum, Borage Family) grows on Mt Diablo in a single colony along North Gate Road. The flowers of the species are very distinctive. Look for the white flowers (with a purple tinge) that form a coil. This is a sprawling plant of summer, perhaps a recent colonizer of the mountain.
Narrow petal Stonecrop (Sedum Radiatum, Stonecrop Family) is found on Mt Diablo in the North Peak-Mt Olympia area. This species is more upright, with narrower leaves, than the more common Sedum Spathufolium. One specimen was collected during an unrelated butterfly census project. It is a host plant of an undescribed butterfly, a subspecies of Moss Elfin (Incisalia Mossii).
Ammannia sp. (Loosestrife Family) grows in a small colony at Macedo Ranch. The species has yet to be positively identified, but will most likely be a first county record! The flowers are purplish and have four petals per flower, growing in whorls around the stems. The whole plant turns red in the autumn. It blooms in summer after the soil has dried.
Alkali Mallow (Malvella Leprosa, Mallow Family) was recently discovered at Macedo Ranch and is poorly established. This is a sprawling plant with grayish-green leaves that are kidney-shaped. The flowers are small and creamy yellow, blooming in summer.
Wavyleaf Paintbrush (Castillija Applegate: ssp. Martinii, Figwort Family) is only found on Mt Diablo in the Donner Canyon area, where it is rare. Note that the leaves are bright green and sticky to the touch.
Salt Grass (Distichlis Spicata, Grass Family) grows in a colony along North Gate Road at a sodium carbonate seep. The leaves resemble those of Bermuda Grass. This species tolerates high levels of salt in the soil.
Southern Cattail (Typha Domingensis, Cattail Family) was identified from a previously-collected specimen from North gate Road. This species probably also grows at South gate Road and Pine Canyon. In this species the male and female portions are separated by a gap, and the leaves are more narrow than in Typha Latifolia.
The above species are all native and probably occur naturally here, though a few may trace their origin to recent construction or weed suppression. The following non-native and introduced native plants are also additions to the Mt Diablo floral list. These introduced plants are far more extensive in both number of species and number of individuals, often displacing native species to the point of local extinction. Many of the following are aggressive, unwanted species in this ecosystem.
Hedge Parsley (Torilis Arvensis, Carrot Family) is a common widespread species on the mountain. It has an inconspicuous white flower. It is difficult to identify, except by its fruit, from several similar species.
Cardoon (Cynara Cardunculus, Sunflower Family. is an invasive type of artichoke found at the Three Springs area, Pine Ridge and Wall Ridge. It has brilliant blue-purple flowers. There has been some effort to control this species on the mountain.
Salsify (Tragopogon Porrifolius, Sunflower Family) grows in small numbers around Rock City and Mitchell Canyon. Note the Solitory flowers and a white milky sap.
Wild Radish (Raphanus Sativus, Mustard Family) and Jointed Charlock (Raphanus Raphanistrum) sometimes hybridize, forming a confusing complex. Members of this complex are common on North Gate Road. The blossoms can be white, yellow or pinkish-purple.
Eastern Rocket (Sisymbrium Orientale, Mustard Family) was recently found growing along South Gate Road. It may also grow on North gate Road. It resembles Hedge Mustard but has very long seed pods that look like missiles (hence the common name).
Bird’s-foot Deerweed (Lotus Corniculatus, Pea Family) is an invasive species found in Pine Canyon, especially along Pine Creek. The flowers are orangish-yellow.
Spanish Broom (Spartium Junceum, Pea Family) is found along Pine Creek in Pine Canyon. It has conspicuous yellow flowers that contrast with the bare green branches. there probably will be an attempt to control the species on the mountain.
Shamrock (Trifolium Dubium, Pea Family) grows in Mitchell and Pine Canyons. The tiny flowers are yellow and resemble beehives.
Rose Clover (Trifoliom Hirtum, Pea Family) is a common species along North Gate Road, Pine Canyon, etc. The flowers are conspicuous and vary from rose pink to deep pink.
Spring Vetch (Vicia Sativa, Pea family) is common and widespread on Mt Diablo. The flowers are usually a combination of pink and pale purple.
Winter Vetch (Vicia Villosa, Pea Family) is an abundant species in the Pine Canyon area. The flowers are a deep shade of purple. This species is aggressive in its growth habit.
Dove’s-foot Geranium (Geranium Molle, Geranium Family) is common and widespread on the mountain. In appearance it closely resembles Geranium Carolinium.
Clasping Henbit (Lamium Amplexicaule, Mint Family) is rather local on Mt Diablo. It grows in Mitchell Canyon and Knobcone Point Road and sometimes in Pine Canyon. The flowers are pinkish-red, and the circular leaves grow around the stem.
Himalayan Blackberry (Rubus Discolor, Rose Family) grows in Pine and Donner Canyons. It resembles Rubus Ursinus, but note it often has leaflets in S’s and has stouter spines.
Puncture Vine (Triblus Terrestis, Caltrop Family) grows along South Gate Road, where it is uncommon. This species has yellow flowers and hugs the ground, Bicyclists learn to avoid its spiny seed pods that give it its common name.
English Plantain (Plantago Lanceolata, Plantain Family) is found at Macedo Ranch and probably elsewhere. the leaves of this species are long and narrow and look shiny. It has an inconspicuous whitish flower at the end of a tall stalk. This species can tolerate heavy foot traffic.
Big Quaking Grass (Briza Maxima, Grass family) grows in abundance at Rock City and Pine canyon (probably widespread). The seed head looks like the rattle of a rattlesnake.
Hedgehog Dogtail (Cynosurus Echinatus, Grass Family) is a common widespread species on Mt Diablo. The seedhead somewhat resembles the European Hedgehog (a small mammal). This plant species has quickly spread in the park.
The changes in the floral composition of Mt Diablo are the result of many factors. Exotic species, sometimes also native ones, often establish themselves in disturbed areas. This is often due to cattle grazing, construction and weed control, creating an unnatural habitat where aggressive plants can dominate as pioneering species. This is perhaps the single most important point concerning the change in species composition. Many of the "new" species to the mountain appeared recently, and probably were not in this area prior to Bowerman’s 1944 Flora. Some of the new discoveries are the result of better access to remote areas, or searching these areas during a different season. A few of the new discoveries are the result of re-examination of previously-collected specimens or changes in plant taxonomy. The Revised Flora of Mt Diablo will be more complete and more useful to anyone interested in the mountain’s flora.