The waxy epidermis that helps the Desert Candle conserve water in its desert habitat has made it an important part of the culture of the Chihuahuan Desert. Native Americans used Desert Candle to extract a homemade sealing wax. The plant became economically important in the desert of Texas and Mexico around 1900, when it was exploited to produce commercial sealing wax and phonograph records. Its Spanish name, "Candelilla" (pronounced "can-deh-LEE-ya"), means "little candle." It’s also known as the "Wax Plant" in the United States.
Today, the wax industry markets the Desert Candle as a component in sealing waxes, paint, varnish, paint remover, cements, cosmetics, leather dressing, fireworks, lubricants, waterproofing compounds, casting wax, crayons, adhesives, dyes, candles, electrical insulating compounds, sizing, celluloid, waterproofing agents, soft wax stiffeners, furniture polishes and other polishing compounds, chewing gum, candies, and wax cheese and fruit coatings. Desert Candle wax contains mostly hydrocarbons, esters and fatty acids and alcohols in proportions that make it hard, lustrous, brittle and slightly tacky.
Desert Candle belongs to a genus of plants (Euphorbia) that contain a latex that has been identified as a possible source of latex for rubber production. As its formal scientific name, Euphorbia antisyphyllitica, suggests, the plant was thought to be useful in the treatment of syphilis. It is a diuretic, helping alleviate some of the discomfort caused by this disease. However, its latex is poisonous, and the plant contains carcinogenic compounds.
Today, Desert Wax products come from Mexico, where it’s more abundant. Mexican campesinos harvest the entire shrub, leaving the roots so that it regenerates within a few years. Producers extract the "cerote" (wax) by heating the plants in water with sulfuric acid. The wax floats to the solution surface, where workers skim it off and allow it to cool. The remaining plant tissues, dried in the sun, become the firewood to heat water for the next batch.
The crude wax first appears on the market as lumps sold to companies that refine it, re-heating it and passing it through a filter press to remove impurities. Filtered and bleached Desert Candle has a light yellow color and finally appears to manufacturers in the form of slabs, blocks, lumps, pellets ("pastillas"), powder or flakes.
Ecology of Euphorbia antisyphillitica
Desert Candle grows in clonal groups. Its above-ground structures are cylindrical, leafless stems with a waxy green-gray appearance, like a candle. It grows up to three feet tall, and produces tiny, inconspicuous pink-white or cream colored flowers that grow in clusters along the stem. Euphorbia antisyphillitica belongs to a plant family rich in species in the arid southwestern desert: the euphorbs (Euphorbiaceae). This group, rich in species diversity and containing several economically important species, is taxonomically complicated and poorly studied.
Desert Candle grows in areas of Trans-Pecos Texas such as Big Bend National Park, where hard frosts are rare. It’s endemic to the Chihuahuan Desert, and, beyond West Texas, it occurs in the Mexican states of Chihuahua, Coahuila, Zacatecas, San Luis Potosi and Durango, where its habitat is abundant.
Because it grows in hot, dry areas, where water is the principal factor limiting plant growth, the plant’s waxy epidermis helps it reduce water loss from its tissues. This species, like many other species of euphorbs, does not produce leaves, and its pencil-like stems carry out the photosynthetic process. The lack of leaves also helps the plant reduce water loss by reducing its overall evaporative surface area because cylindrical surfaces of stems have a much lower surface to volume ratio than planar (flat) surfaces of leaves.
Likewise, the plant’s tiny, inconspicuous flowers also help avoid excessive water loss. Wind carries the pollen of these tiny, pink-white colored flowers from one plant to another. Later, when seeds mature, they explode from the dried fruit.
Desert Candle, like many desert plants, has fibrous roots that penetrate the growing substrate and help the plant absorb water from the rocky soils where it grows. They also reproduce vegetatively from their roots, giving them an important advantage after harvest activities.
Although the unrefined plant contains toxic compounds that make it resistant to grazing by many species of mammals, it is important as habitat and a food source for a variety of invertebrates. It is also an abundant component of biomass in the rocky, dry soils where it’s found. Its clonal form and fibrous root system help reduce runoff from desert pavement, and its tissues store water in this extremely arid environment.
The plant is used as an ornamental in xeriscapes, but, because it is not cold hardy, it must be protected from hard frosts when used outside of its natural range. Aside from this drawback, the plant is attractive for garden use. It requires little water and maintenance, and its unusual appearance and waxy green coloration make it a texturally interesting addition to rock gardens.
Desert Candle also grows well as a potted plant outside of its natural range, if protected from hard frosts. One may propagate the plant by seed or cuttings taken any time during the growing season. Even dormant plants take from cuttings. Seeds should be sown in a warm greenhouse in the spring. Cuttings should be allowed to dry and form a callus before planting. Plants will last up to two weeks outside their substrate before replanting. Although plants require little maintenance once established, they do require water during the growing season (late summer and early fall in the Chihuahuan Desert).
The Desert Candle, plain and simple at first glance, is a fascinating survivor in the harshest of desert environments. It’s become an important part of the Chihuahuan Desert heritage because of its economic and ecological impact, and study of this unusual genus of arid land plants could reveal even more interesting and useful results.
About the author: American born Jeffrey R. Bacon is a professor and research scientist at the Universidad Juárez del Estado de Durango, in Durango, Durango, Mexico. He currently teaches Ecology in the University's Escuela de Ciencias Químicas and carries out reaseach related to Mexican oak systematics and floristics in the Área de Ecología Forestal, at the University's Instituto de Silvicultura e Industria de la Madera. Bacon curates the University's Herbarium as part of his research. He has lived and worked in Durango since 1994.