By Ellen Dean
This month’s rare plant lives within the newly designated Chuckwalla National Monument! Orocopia Mountains spurge (Euphorbia jaegeri) is a short, delicately branched shrub that is endemic to (only found in) California’s Mojave Desert in Riverside and San Bernardino counties. OM spurge grows within desert scrub vegetation on dry rocky hillsides or arroyos with granitic, metamorphic, or calcium-rich substrates. It has fancy tastes.
Spurge family (Euphorbiaceae) expert Victor Steinman and James André, directorof the Granite Mountains Desert Research Center, published the name Euphorbia jaegeri as new to science in 2012; it was added to the Rare Plant Inventory in 2013. Currently, OM spurge is known from approximately 13 populations, around 10 of which are found in the Orocopia Mountains of Chuckwalla National Monument. The other three populations are located in the Marble and Bristol mountains of San Bernardino County.
Orocopia Mountains spurge has a California Rare Plant Rank of 1B.1 (rare in California and elsewhere and highly threatened). At the time this species was described in 2012, it was threatened by both mining activities and large-scale wind power development, especially in San Bernardino County. Its protection within the Chuckwalla National Monument in Riverside County is good news!
The spurge family is a large family of flowering plants. Although it is best represented in the tropics, spurges thrive in many different habitats worldwide. In California, 85% of Euphorbiaceae species live in our deserts. Some of the interesting characteristics of the genus Euphorbia are its white latex (sometimes causing dermatitis!) and its unisexual flowers that are borne in clusters within a cup-shaped structure (involucre) that sometimes has interesting appendages and glands along its rim. In OM spurge, the appendages are white to pink and lobed; sometimes people mistake them for petals. The female flowers are a stalked ovary that develops into an enlarged three-parted fruit that hangs over the edge of the involucre. The male flowers are individual stamens that are crowded within the cup. OM spurge flowers from October through March, but you’ll need a hand lens or magnifying glass to examine the wonder of this tiny group of flowers, as the involucre is only 1.5 mm wide!
Pro tip: A reliable place to find this plant is on mountain slopes and arroyos south of Interstate 10 in the Chuckwalla National Monument! Visit the Rare Plant Inventory to learn more about Orocopia Mountains spurge.
Ellen Dean is Associate Rare Plant Botanist at CNPS, helping complete rare plant profiles. In a previous life, she was an herbarium botanist, performing plant IDs, leading collecting field trips, training students in plant identification, curating the herbarium, and publishing taxonomic papers.
