Cliff Spurge

Like its cousin the poinsettia, cliff spurge (Euphorbia misera) lacks true petals. Instead, the flowers are tiny and inconspicuous. In poinsettia, small flower clusters are surrounded by colorful leaves, which look like petals. In cliff spurge each tiny cluster is surrounded by small but showy dark red nectar glands, each of which has a pale, fringed wing. The ring of glands gives each flower cluster a perky, happy appearance, making one wonder about the appropriateness of the Latin name misera, or wretched.

Cliff spurge is classified as rare and endangered in California, where it is threatened by development, fire and and by non-native plants. It is somewhat more common in Baja California. Cliff spurge prefers coastal bluffs and rocky slopes, and although San Elijo Ecological Reserve appears to offer plenty of suitable habitat, the only plant we have found in the Reserve is planted northwest of the Nature Center. Many years ago, former Supervising Ranger Susan Welker started this from a cutting taken from a plant in the Tijuana River Valley.

Description ^{26,59,174,292}

Cliff spurge is a drought-deciduous, woody sub-shrub, irregularly rounded or mounding to two to four feet (60-120 cm) tall and wide. Stems are somewhat succulent and irregularly branched with grayish bark. Young stems are hairy, becoming smooth with age. Leaves often appear clustered. They are oval with smooth margins, less than one inch (2.4 cm) long, somewhat thickened and folded upward along the midrib. Petioles are short and often have two thread-like stipules. The plant contains a milky sap that is a skin-irritant and possibly toxic if ingested.

What appears to be a single flower is actually a cluster of one female flower surrounded by male flowers; this is called a cyathium and characterizes many species in the Euphorbia genus,⁴¹ although even within the genus, there is a lot of variability in cyathium form.⁴⁶⁹  In cliff spurge, the cyathia occur singly at the ends of short branches. The base of the cyathium, the involucre, is a cup-shaped structure composed of five fused bracts. Surrounding the central flowers, and appearing to be petals, are five dark red or maroon to purple nectar glands, each with a narrow, white or yellow, irregularly-incised wing. Neither female nor male flowers have sepals or petals. A male flower consists of a single stamen with two rounded anthers. The female flower consists of a single pistil held above the involucre by a stalk; there are three forked styles with dark red-purple stigmatic surfaces. The ovary develops into a grayish, lobed and wrinkled fruit that contains one grayish, wrinkled seed.  The primary bloom season is January – August¹  but flowers may occur any time, especially after a rainfall.

Classification ^{11,44,59,143,306}

Cliff spurge is a dicot angiosperm in the spurge family (Euphorbiaceae), a large, diverse group containing small herbs, vines, cactus-like succulents, shrubs and trees. Many euphorbias contain a clear or milky sap that is irritating or toxic. Many have nectar glands outside the flowers. Flowers often lack petals, although some species have colorful bracts or glands that function as petals. Flowers are unisexual. Male and female flowers may be on the same plant (monoecious) or on separate plants (dioecious). The male flowers may have one or numerous stamens. The pistil of the female flower may have three styles; the ovary is superior, usually three-lobed, and it ripens into a dry three-chambered capsule that splits open on maturity releasing one seed per chamber. Seeds often have a fleshy appendage at one end.

The spurge family contains a variety of decorative, useful and annoying species. These include the deadly castor bean (Ricin ricinus), the beautiful poinsettia (Euphorbia pulcherrima), the entertaining Mexican jumping bean (Sebastiania pavoniana), the important rubber tree (Hevea brasiliensis) and the omnipresent garden weed, spotted spurge (Euphorbia maculata). Other native family members in the Reserve are California croton (Croton californicus), doveweed (C. setiger), rattlesnake weed (Euphorbia albomarginata) and matted sandmat (E. serpens)

The genus Euphorbia is one of the largest angiosperm genera, with the number of species estimated near 2000.^44,306 Spurges are characterized by their unique flower structure, the cyathium, in which highly reduced male flowers, each consisting of a single stamen, surround one highly reduced female flower, consisting of a single pistil. These are clustered in a cup-like involucre which is surrounded by colorful nectar glands. Together the structure resembles a single flower.

Ecology  

One defining characteristic of the spurges is the presence of a white or clear sap, which ranges from irritating to toxic. Why does a plant group invest any energy in sap production? How does the sap benefit the plant?

In some species, the sap has been shown to have antifungal and antibacterial activities.⁴⁷⁰ Also, this sap dries very quickly into an impermeable barrier. While we have found no scientific studies, it has been suggested that these properties combine to help the plant resist infection and heal after injury. The latex may also serve to repel herbivorous insects and grazers.⁴⁶⁹

Human Uses  

Species of spurge have been widely used in herbal medicine around the world. One summary of a wide spread tropical species, thought to be native to India⁴¹ (E. hirta) reports the production of over 17 active compounds. Spurges have been used for a variety of ailments ranging from digestive problems and respiratory ailments, to jaundice, tumors and pimples. It is used as a poison for arrows. Generalization within the spurges is complicated by the large size and variability of the genus, and by its complicated taxonomic history.

We have found no reports of use of cliff spurge, specifically. In southern California, native Americans used the related spotted spurge (Chamaesyce maculata, formerly Euphorbia maculata) as treatment for rattlesnake bites,^15,17 but it is risky to attribute this property to E. misera.

Many of the botanical discussions are accompanied by stern warnings: “Most Euphorbias and many of their close relatives have very caustic juice that may cause blisters and should never be put in the eyes or taken internally”¹⁵; “… never eat any part of this plant – it’s toxic”²⁹²; “Large doses have a depressant effect on the heart and can kill you.”³¹⁰

Interesting Facts ^21,41,59

The genus, Euphorbia, was named by King Juba II, the king of Mauritania between 25 BC and 23 AD, in honor of his Greek physician, Euphorbius. The species name, misera, comes from that word in Latin, which means “wretched, worthless, or vile”. Presumably, this reflects the sad appearance of cliff spurge in the summer, after it has dropped its leaves.

The common name, spurge is derived from the Middle English/Old French espurge, which mean “to purge”, and refers to the use of some spurge’s sap as a laxative.