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Euphorbia lomelii

Accession Count: 441
Common Name: lady slipper
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Family Name: Euphorbiaceae
Botanical Name: Euphorbia lomelii
Synonyms:
Botanical Synonyms: Pedilanthus macrocarpus
Sub Species:
Variety:
Forma:
Cultivar:
Characteristics: Euphorbia lomelii is an upright, succulent perennial with thick (up to three-quarters of an inch in diameter), jointed and sometimes branched, light green stems that grow up to 6
feet tall from a woody root crown (1,2). The stems are often coated with a
thick waxy film, resulting in a frosted appearance (1,3). Small, oval-shaped apical
leaves, measuring approximately three-eighths of an inch long and one-eighth of an inch wide, occasionally appear, only to drop quickly as they are drought deciduous, usually leaving the thornless stems,
which are capable of performing photosynthesis, bare and leafless (1,4). As is
characteristic of Euphorbia species,
the stems, when cut, exude a milky sap, which can be toxic to humans and
animals if ingested in quantity (1,3,5,6). Flowering structures, ranging in
color from red to peach to yellow, appear in clusters at the tips of stems,
with a single female flower surrounded by several male flowers in each cluster
(3). This flowering structure, known as a cyathium or an involucre, is composed of a lower pair of bracts and an upper,
more complex part called the spur, which is formed by a gland chamber that
secretes nectar (7). The female flower first emerges and grows straight out,
but is gradually pushed down and away as the male flowers develop perpendicular
to it, probably to discourage self-pollination (8). The male flowers,
which are most conspicuous, measure up to 1” in length. The flowering structure
is said to bear a resemblance to various objects: to shoes or slippers, hence the
common English name slipper flower, the genus name Pedilanthus, and a Spanish name, zapato del diablo (“devil’s shoe”); or to birds, the source of another
Spanish name for it, gallito (“little
rooster”). Red, oblong fruit develop from female flowers and are visible in the
fall (4). 
Compound: Eup lom
Geographic Origin: American Tropics
Ecozone Origin: Neotropic
Biome Origin:
Natural History: Similar to other species of the genus Euphorbia, which contains 13 species, Euphorbia lomelii is endemic to
the New World (7). This genus is distinguished by the morphology of its
flowering structure (the cyathium), considered to be the most specialized of all
succulent Euphorbia species (7). The
complexity of the cyathium is due in part to the recessed position of its gland
chamber, which cannot be reached by insects, and it is believed that this
structure evolved as a special adaption for hummingbirds (7,9). In its native
environment, E. lomelii is
generally pollinated by Costa’s hummingbird (10), but will attract others as
well (5,11,12). A true desert species, the plant can be found growing naturally
along washes and on plains and rocky slopes on the Baja California peninsula,
on several Gulf of California islands, and on the Mexican mainland from Sonora
to Colima (2,5,10,11). It is frequently observed growing
in partial shade provided by cacti and other desert plants (3). Its desert
adaptations include the waxy film on its stems and the small, ephemeral leaves,
both of which help it conserve water. The plant’s scientific name results from a
combination of several Greek words: the genus name from pedilon, meaning “shoe,” and anthos,
“flower,” and the specific epithet from makros,
“large,” and karpos, “fruit” (1). The
classification of the plant has changed several times (7), including the most
recent emendation, which took place in 2003 when the Pedilanthus genus was folded into the Euphorbia genus (6) and Pedilanthus
macrocarpus was renamed Euphorbia lomelii
(13) based on DNA sequencing (14). This new name, however, has yet to gain
widespread acceptance.
Cultivation Notes: With its unique growth form, Euphorbia lomelii can bring a wonderful accent to any desert garden. Use it where
upright growth is desired or where contrast with dark green plants will be most
striking (2). Plant in full sun or partial shade to maintain its upright form as it
may take on a more sprawling character in full shade (4,5). It tolerates desert
heat well, but should be protected in cold weather as it will be damaged at
28°F or below (4,5,12). When low temperatures are regularly in the 30s or 40s,
it may begin to show chilling injury indicated by a reddening of its stems (4).
To avoid cold damage it may be planted against a south-facing wall, in a
courtyard, or in a container that can be moved indoors when low temperatures
are expected (5). Cultivars that have been bred to withstand lower temperatures
are available. This plant does not have thorns and can be used as a poolside plant (12), but it is best planted
out of high traffic areas since its stems may be brittle and break with
frequent contact. It is easy to propagate from seeds or stem cuttings and requires little
maintenance (4,7,11). It tolerates most soils as long as they are well-drained
(11). Once established, it will sprout new stems from its root, gradually increasing
its girth over time (5). It takes pruning well, and may be cut back anytime as
needed (4). Water twice a month during the summer, but avoid watering during
dormancy in the winter to reduce chance of crown rot or root rot (5). 
Ethnobotany: In addition to being used as a cultivated species, Euphorbia lomelii has demonstrated benefits in other ways.
Native peoples cooked the stems to obtain wax to make candles (10), which is,
incidentally, the source of another name for the plant in Spanish, candelilla (“little candle”), a name given
to several species of the genus Euphorbia
in Mexico. This wax is also used in cosmetics, varnishes and lubricants (1). In recent years,
studies have been undertaken to determine the feasibility of developing E. lomelii into a large-scale
crop for wax production, and suggest that a 2% yield of wax could potentially
be achieved, yielding up to 700 kilograms of wax per hectare (15). As with
other species of the Euphorbia genus
(6), the milky sap can induce severe diarrhea (10). (“Spurge,” a common name for
many Euphorbia species, ultimately
derives from the Latin expurgare, “to
purge or cleanse,” and its effects in this aspect were known to the ancients [6,16].)
The sap from the plant was also used by native people to treat chapped lips,
cuts and burns (10). Studies in recent years indicate that the sap renders as
much as 6-10% of its fresh weight in purified rubber, suggesting that the plant
could potentially become a commercial rubber source (17). 
Height: 0 - 5 feet
Width: 0 - 5 feet
Growth Rate: Moderate Growing
Grow Season: ForeSummer
Flower Season: Spring
Color: Red
Function: Accent
Spread: Non-spreading
Allergen: Allergenic
Invasive: Benign
Toxicity: Benign
Hardy: Semi-hardy
Water Use: Low water Use
Citations:
  1. Mora Bravard
  2. Mielke, J. (1993). Native Plants for Southwestern Landscapes. University of Texas Press. 
  3. Candelilla
  4. Virtual Library of Phoenix Landscape Plants
  5. Arizona-Sonora Desert Museum
  6. The Euphorbia Project
  7. Koutnik, D. (1985). “An Introduction to the Genus Pedilanthus.” The Euphorbia Journal, vol. 3. 
  8. Felger, R. and Wilder, B. (2012). Plant Life of a Desert Archipelago: Flora of the Sonoran Islands in the Gulf of California. University of Arizona Press. 
  9. Trager, J. (1986). “Cases of Convergence.” The Euphorbia Journal, vol. 4. 
  10.  Roberts, N. (1989). Baja California Plant Field Guide. Natural History Publishing Company. 
  11. Arizona cooperative Extension
  12. AMWUA
  13. Tropicos
  14. The Spurge Page
  15. Scora, G. and Scora, R. (1999). “Epicuticular hydrocarbon composition of gallito (Pedilanthus macrocarpus) from Baja California and Sonora, Mexico. Industrial Crops and Products. 
  16. Rowley, G. (1984). “The Succulent Spurges: Landmarks in Early History, Part 2.” The Euphorbia Journal, vol. 2. 
  17. Sternburg, C. and Rodriguez, E. (Feb. 1982). “Hydrocarbons from Pedilanthus macrocarpus
  18.  (Euphorbiaceae) of Baja California and Sonora, Mexico.” American Journal of Botany. 
  19. Jones, Warren D, and Charles M Sacamano. Landscape Plants for Dry Regions: More Than 600 Species from around the World. Fisher Books, 2000.
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Euphorbia lomelii