The Spurge Page
Euphorbiaceae

Euphorbia antisyphylitica  Zuccarini 1832 (Candelilla plant)
growing at the Langtry visitor center, Texas. The epiphet antisyphylitica refers to the plant's supposed medicinal properties. The flowers are relatively decorative by the standard of many Euphorbias. This plant is relatively common in the Big Bend country and the Rio Grande valley but in its natural habitat, where water may be scarce and the heat intense, the stems often have a bronzed appearance.
 
The candelilla plant was an important source of candelilla wax, which is still produced in small quantities by boiling large quantities of stems with sulphuric acid, and skimming the wax from the surface of the vat. The wax was used in the manufacture of phonograph records, in cosmetics and as an industrial lubricant.

Unfortunately, much of the plant material required for processing is harvested from its native habitat putting pressure on plant populations.

Euphorbia clavarioides  Boissier 1860 (Lion's Spoor)
a small caudiciform Euphorbia popular with growers of alpines. Native to mountains of Botswana and South Africa where it grows at elevations of 4800-8800 ft. In the very strong light of its habitat, the arms are short and compact forming a hemispherical cushion with small yellow-green flowers.
The plant tolerates cool, frost free winter conditions. The sap may irritate the skin.
Photographed in the Alpine House at RBG Kew.

Euphorbia caerulescens  Haworth 1827 (Sweet Noor)
A columnar, branching Euphorbia with 4-6 angled blue-green stems furnished with pairs of brown thorns along the vertices. Clusters of small yellow flowers on the stem vertices around the growing point are followed by pink berries. The bushes grow 5 - 10 ft tall and spread by stolons.
 
Although the milky latex is poisonous, dry stems can be used as fodder. Native to the Noorsveld area of Cape Province, South Africa.

Left: Euphorbia enopla  Boissier 1860   from the Eastern Cape forms 3ft tall clumps of 6-7 angled or ribbed branching, fat stems with red spines along the apex of the ribs. Spines are old flower peduncles. Small vestigial leaves are produced near the growing points.
 
Similar plants:
Euphorbia ferox  Marloth 1913   is similar to Euphorbia enopla but with fatter stems.
Euphorbia heptagona  Linnaeus 1753   from the Western Cape forms 10 ft bushes of tall, branching 7-11 angled or ribbed stems with green, brown or grey spines along the ribs.

Euphorbia esculenta  Marloth 1909 (Vingerpol) - one of the "caput-medusa" Euphorbias. A substantial central caudex up to 8 in diameter is surrounded by many fleshy arms patterned with shallow tubercles. Flowers around the growing points are fluffy white tufts with yellow stamens and surrounded by small brown bracts.
 
Although the epithet "esculenta" means "edible" this plant should be regarded as poisonous. However it is used as cattle fodder. Native to the South-Eastern Cape Province, South Africa.

Euphorbia fortissima Leach 1973
A columnar, branching Euphorbia with blue-green stems to 20 ft tall.
Native to Zambia and Zimbabwe, along gorges of the River Zambezi below Victoria Falls.

Euphorbia griseola var. griseola  Pax 1904
Sprawling shrubs with thin (half-inch), branching, 4-6 angled spiny stems about 3ft tall. Tiny yellow flowers are produced near the ends of the stems.
 
Native to Northern South Africa, Southern Zimbawe, Mozambique and Botswana.

Euphorbia hamata  Sweet 1818
Shrubby plants with a tuberous root. The thick fleshy, tuberculate stems are spineless and produce vestigial leaves and small green to reddish flowers at the growing points.
 
Native to Namibia and the Northern Cape. Reported to be cold tolerant.

Euphorbia horrida  Boissier 1860 (African Milk Barrel)
from the Wittepoort Mountains of the Great Karoo. This spiny clumping plant has angular stems up to 18 in tall and with up to 20 ribs. This species is somewhat variable and selected cultivars are known with dark-green to glaucous-grey plant bodies, different degrees of spination or with red spines and flowers.
 
The long peduncles (stalks) of the small male and female yellow-green flowers produced on the ribs near the growing point, desiccate to become prominent rows of rigid spines up to 2 in long. The white sap is very poisonous.

The habitat of Euphorbia horrida receives both winter and summer rainfall. However it is advisable to withdraw water from cultivated plants during cold weather. The plants tolerate a touch of light frost if bone-dry. Strong light is necessary to prevent the stems from becoming unnaturally elongated. This Euphorbia is a host for the parasitic mistletoe Viscum minimum.

Euphorbia meloformis  Aiton 1789   Syn: Euphorbia valida  NE Brown 1915
Spheroidal plant bodies with prominent ribs or angles, attractively striped in shades or green and with prominent branched peduncles (old flower stems) along the vertices. The plants may become columnar or clump with age. The peduncles of Euphorbia meloformis ssp. valida are more persistent than for E. meloformis. Plants generally produce either male or female flowers. As with many Euphorbias the dry seed capsules are explosively dehiscent as a mechanism for scattering the seed.
 
This slow-growing species is native to the Cape Province of South Africa. Best in full sun to light shade. It tolerates a cool, dry winter when it is dormant.

Euphorbia milii des Moulins 1826 (Crown of Thorns)
named for Baron Milius, governor of the island of Bourbon
from Madagascar but spread across the Middle East in ancient times. This spiny, woody shrub produces small oval green non-succulent leaves, mainly near the ends of the stems and falling off older growth or when environmental conditions are unsuitable. The small flowers produced throughout the year, are surrounded by a pair of bright red bracts.
 
Numerous selected forms are available with pink, yellow or even white bracts. Several hybrids have been made with other species, especially E. lophogona. Vast numbers of plants are produced in the horticultural trade from cuttings, especially for Christmas. In tropical climates Euphorbia milii is used to make an impenetrable flowering hedge. This plant is not frost tolerant and in my experience dislikes being below 40°F.
 
Legend has it that a wreath of Euphorbia milii was the Crown of Thorns worn by Christ at the crucifixion. However, an alternative candidate native to Palestine is the non-succulent woody shrub Paliurus spina-christi "Christ's Thorn".
 
Left: Euphorbia milii var. splendens (Crown of Thorns) - a more robust form of this classic spurge, with larger flowers a thicker stem and shorter, triangular thorns.
Right: Euphorbia milii var. imperatae a form with yellow flowers, tending to fade to a slightly pink tint.

Euphorbia obesa Hooker 1903
a rare globose plant becoming columnar with age, from the Karoo in the Eastern Cape of South Africa. The typically 8-angled single stem is easily grown to about the size of a cricket ball and will grow much larger to a 10 in column, rarely offsetting. It is challenging to keep mature plants from becoming corky around the base or from collapsing during the winter. In a strong light the plant body, usually gray-green with purple banding, becomes bronzed.
 
Tiny yellow flowers are produced freely near the growing point. Some plants produce only male or female flowers; others produce both. The flowers are followed by explosive, angular seed capsules which must be covered with fine mesh before they ripen if the seed is to be collected.
 
Euphorbia obesa is a favourite with succulent-plant enthusiasts and although rare in its habitat is common in collections. However, as it hybridises freely with other Euphorbias many cultivated plants may not be pure bred and this may explain many oddities and divergence from normal growth patterns such as offsetting.
The smaller globose plant E. symmetrica has been reduced to sub-species status: E. obesa ssp. symmetrica.

Euphorbia polygona  Haworth 1803
a spiny columnar plant to 18 in tall, clumping from the base. The stems may have up to 20 ribs with spines (old flower stems) along the ribs. The degree of spination and body colour varies. Small purple flowers with yellow stamens are produced along the ribs near the growing point.
 
Native to the Eastern Cape of South Africa. Selected cultivars have no or minimal spines and a glaucous grey body (E. polygona 'Ghost', 'Snowflake'). This Euphorbia is a host for the parasitic mistletoe Viscum minimum.

Euphorbia pugniformis  Boisser 1862 Syn: Euphorbia caput-medusae Linnaeus 1753
One of the "caput medusa" Euphorbias from the Western and Eastern Cape of South Africa. The globose plant body is surrounded by many tuberculate arms. Each tubercle produces one vestigial leaf.
 
Cristate forms are known and are propagated from cuttings and grafts. The sap is an irritant and a violent emetic.

Euphorbia resinifera   Linnaeus 1753 (Euphorbium Officinarum)
is the spurge of antiquity, known to the Greek physician Dioscorides (40-90 AD) and Pliny the Elder (23-79 AD) for its purgative sap (euphorbium). This is probably the thorny plant from Mount Atlas in Morocco recorded by King Juba II of Mauretania (ca. 50 BC- 19 AD). The King is said to have named the plant "Euphorbea", after his rotund Greek physician, Euphorbus. The name was later formalised by Linnaeus (Species Plantarum, 1753) as the official botanical name for the genus.
 
Euphorbia resinifera forms multi-stemmed mounds of four-angled succulent stems, whose edges are furnished with short pairs of brown spines spaced about half an inch apart. The ends of the stems produce bright yellow flowers along their edges.
 
Euphorbia resinifera is easily grown in a Mediterranean climate but may become a noxious weed in some places. It is readily propagated from cuttings. All parts are toxic, but the resin (dried sap) has been used as an extreme purgative and wood preservative.

Euphorbia suzanne  Marloth 1929
a small caput-medusa style Euphorbia from the Karoo, makes a handsome specimen given sufficient time. This plant developed a cristate main head although it grew as a normal plant for many years.
 
In their habitat, the plants are sunk into the ground with the space between the main head and the side stems covered in grit or debris. However, plants in cultivation need to be raised to keep them healthy. This one is grown in diffuse sunlight behind other shrubby spurges.

Euphorbia suzanne tolerates a cool, frost-free winter provides it is kept dry. It should be planted in a very gritty mixture with plenty of crocking at the bottom of the pot. Water sparingly, especially when dormant.

Euphorbia tirucalli  Linnaeus 1753 (Pencil Tree, Milk Bush, Kraalmelkbos)
possibly the "Sticks on Fire" cultivar from the Huntingdon Botanic Garden. Another selected cultivar "Firesticks" colours up to an even brighter red, making a fine display of colour.
 
Euphorbia tirucalli grows with one or more woody grey-brown trunks up to 30 ft tall, supporting brush-like masses of green succulent cylindrical branches about as thick as a pencil. Vestigial leaves are tiny and rapidly shed. The tiny yellow flowers are clustered on the branch tips. Euphorbia tirucalli is widely distributed on poor and salty soils, from North-Eastern to Southern Africa and Arabia. It has been naturalised in many tropical countries including India. It will not stand any degree of frost.
Photo: M. Fields 2010, at J. Paul Getty Museum, Los Angeles.

The milky sap of many Euphorbias is generally an irritant, but that of Euphorbia tirucalli is notably corrosive. Contact with skin may cause burning pain and irritation. Contact with the eyes may cause temporary or permanent blindness. If contamination of the eyes occurs, flush them with water for several tens of minutes and summon medical assistance. Swallowing the sap is potentially fatal.
 
Euphorbia tirucalli is used as an impenetrable hedge or livestock enclosure. Fishermen put macerated branches into streams, where the sap stuns the fish making them easy to catch. The sap can be converted to an oil substitute. Cultivation of this plant on otherwise useless land has been proposed as a sustainable source of energy. The plant is also widely used in traditional medicines as a cure for sexual impotence, an antidote for snakebite and to cauterise skin lesions and tumours.

Euphorbia willmaniae  Marloth 1931
A low-growing plant whose tuberous root produces masses of tuberculate stems, spreading by stolons. Note cristate portion.
 
Native to Namibia and the Northern Cape.

Jatropha dioica  Sessé 1794 (Dragon's blood, Leatherstem)
These xerophytic low shrubs are growing on limestone South of Shafter, Texas. Roots are orange rhizomes, spreading by stolons to form colonies a few feet in diameter. The infrequently-branching, rubbery stems bear clusters of narrow leaves on short spurs. When damaged, the stems exude a clear sap, turning blood-red and which has been used as a red dye. The quarter-inch flowers are pale pink bells clustered at the ends of the stems.
 
Very tolerant of heat and moderate frost. Native to Texas into Mexico, as far South as Oaxaca.

Monadenium heteropodium  Brown 1911
The fleshy green stems are patterned with marked tubercles from which vestigial leaves are produced. Native to Tanzania where it grows on rocky slopes at elevations of up to 3000 ft.

Left: Pedilanthus macrocarpus,  Benthan 1844 (Slipper Plant) from Sonora and Baja California, growing in the Phoenix Desert Botanical Garden. The flowers attract humming birds. This species is an excellent ornamental plant for a container in a warm climate but will not stand any frost.

Left: Pedilanthus tithymaloides  Linnaeus 1753 (Devil's Backbone, Slipper Plant) is a tender climbing shrub native to Florida and the West Indies to Venezuela, but established as an invasive weed throughout the tropics. Young stems carry pointed oval leaves. Often cultivated as a tender ornamental plant. This species grows profusely on poor land and is of interest as a potential biofuel crop.
 
Right: Pedilanthus seed pods. The seeds have been caught by spider webbing.