Common Name: African Milkbush

General Information

Euphorbia tirucalli is an unarmed, succulent shrub or small tree usually growing from 4 - 12 metres tall with some specimens up to 15 metres[]. It has brittle, succulent branchlets around 7mm thick, with white to yellowish latex[]. The plant only has a few, small, deciduous leaves towards the tips of the branches, photosynthesis being carried out mainly by the green stems[, ].
Although poisonous, the plant is commonly harvested from the wild for a wide range of medicinal uses, and also provides several other commodities. It is widely planted for use as a hedge and has long been used in agroforestry systems in east Africa. This is a low-input plant that has high drought and salinity stress tolerance and can be grown on land that is not generally suitable for crops. It has the potential to provide semi-arid zone inhabitants with an energy solution in the form of a biomass that can be converted to gaseous, liquid or solid biofuels[]. This is an ideal species for agroforestry, offering little shade and having many other uses[]. It is also widely planted for ornamental purposes[].
The species is present in all the tropical parts of the world and is common throughout its range. The plant is classified as 'Least Concern' in the IUCN Red List of Threatened Species(2013)[].

Known Hazards

The caustic, irritant sap contains a latex and is highly poisonous, causing severe injury to the eye, irritation and vesication from contact, emesis and purgation from ingestion[, ]. Eye contact with the sap can cause blindness lasting several days[].
The toxicity of the latex is considered seasonal or reduced in young plant parts, and young branches are even roasted and chewed[].
The extracts of the plant contain a number of esters of the tetracyclic diterpenoid phorbol, many of which have been shown to act as tumour promoters (cocarcinogens). Their co-carcinogenic effect on lymphoblastoid cells poses a real threat in Africa where drinking water is drawn around the plants[].
In East Africa the latex is commonly used as arrow poison and as an ingredient for bait to kill rodents and other wild animals; the pulped stems are thrown in water as fish poison[].
In south-western DR Congo the latex has been used in high doses as a trial by ordeal poison; in various countries it is used as criminal poison[].

Botanical References

Range

Dry regions of tropical Africa, though widely grown and naturalised in many areas of the tropics.

Habitat

Normally found in dry bushland thickets and naturalizes easily in brushwood, open woodland and grassland at elevations up to 2,000 metres[].

Properties

Conservation Status	Least Concern
Medicinal Rating
Other Uses Rating
Habit	Evergreen Shrub
Height	5.00 m
Self-fertile	No
Cultivation Status	Cultivated, Ornamental, Wild

Cultivation Details

Succeeds in subtropical to tropical regions at elevations from sea level to 2,000 metres[]. The plant is very well adapted to semi-arid conditions, but also occurs in both dry and moist forest, savannah and shrub land, and also withstands salt stress associated with coastal conditions[]. It grows best in areas where annual daytime temperatures are within the range 25 - 37°c, but can tolerate 12 - 41°c[]. Plants are not tolerant of frost[]. It prefers a mean annual rainfall in the range 400 - 800mm, but tolerates 250 - 1,000mm[]. The plant can grow in areas where the mean annual rainfall can range from 250 - 4,000mm[].
Requires a sunny position[]. Appears to grow on almost any soil type[, ]. Prefers a wide variety of well-drained, light-textured, neutral to acidic soils[]. Prefers a pH in the range 5.5 - 6.5, tolerating 4.5 - 7.5[]. Established plants are very drought tolerant[].
Plants are very tolerant of trimming and also coppice well when cut at 20 - 30cm height. Under semi arid conditions regrowth is excellent[, ].
A density of 10,000 - 20,000 plants per hectare is normal when grown as a fuel crop. When planted at a spacing of 1metre x 1metre it produced 120 tonnes/ha fresh material and 14 tonnes/ha dry matter after 1 year, yielding 40 - 88 kg of crude oil, 135 - 213 kg of sugar and 1.8 tonnes of bagasse[].
There have been plantings of E. Tirucalli in Okinawa which on a spacing of 120cm between bushes are expected to yield 11 - 22 barrels of oil per hectare each year[].
Plants are not resistant to fire[].
Plants usually produce male flowers. Female flowers or plants are much less common. Plants with bisexual flowers also occur, although the female flower apparently often aborts[].

Edible Uses

None known

Medicinal

Caution should be observed in making medicinal preparations of this plant due to its high toxicity[]. Anecdotal evidence suggests that the risks of a lethal overdose are high, particularly when treating children[].
Various studies have shown the presence of a range of active compounds in the plant:-
Euphorbon, which is isolated from the needles, contains 4% caoutchouc[].
The latex yielded 75 to 82 percent resin, and 14 to 15 percent caoutchouc[].
The latex is rich in terpenes, including ingenol and phorbol esters[]. The latter, which is highly irritating, has been shown to be tumour-promoting[].
Six terpenes have been isolated from the plant:- cyclotirucaneol; cycloeuphordenol; tirucalicine; tirucaligine; euphorginol; and euphorcinol[].
The latex showed great similarity in composition and activity to the highly poisonous croton seed oil from Croton tiglium[].

The young branches can be roasted then chewed to relieve a sore throat[]. Ash from the burned branches and stems is used to treat whooping cough[].
The pulped twigs are applied externally to treat oedema of the legs[]. Ash from the burned branches and stems is applied externally as a caustic to treat open abscesses[]. Poultices from the stem are applied to heal broken bones[, ]. Based on the Theory of Signatures, the jointed nature of the plant-stems lead to the use of the plant in SE Asia in a belief that it will assist the healing of broken bones[].

A root and bud decoction is taken as a laxative, and to treat coughs and pectoral pain[].
A poultice of the roots or stems has been applied to ulceration of the nose, haemorrhoids and swellings[, ].

A root-decoction, combined with other drug-plants, is taken in in the treatment of schistosomiasis and gonorrhoea[, ]. The boiled root juice acts as an emetic in cases of snake bite, and is also used for sterility in women[].
Heated root scrapings, mixed with coconut oil, are applied externally to the stomach to relieve stomach-ache[, ].

The caustic latex is vesicant, rubefacient and counter irritant. It is purgative in small doses, emetic in larger quantities[, ]. Two or three drops at a time are given to adults with their food, whilst a dose of 3 - 4 drops is used as a purge to treat ascites and generalised oedemas[]. The potent purgative and emetic properties are employed in Africa in order to treat stomach complaints, constipation, intestinal worms, headache, asthma, epilepsy and palpitations. A few drops of latex are reportedly sufficient to cause vomiting, and are taken in milk as an antidote to poisoning or snakebites[]. Heated branches are chewed and the latex is swallowed to relieve a sore throat and dry cough, but also to induce labour during childbirth[]. The latex is taken in the treatment of sexual impotence and sterility in East Africa, and elsewhere as a sexual stimulant. It is also said to promote breast enlargement[].
The latex is used externally to treat skin-complaints, itches, insect bites, rheumatism, toothache, earache, to raise blisters on syphilitic nodes, and to remove warts, tumours, cancers, etc[, , ]. It is also used for wound healing[, ].
Tthe latex is widely used in Brazil to treat cancer, but in some areas where it is commonly used, tumours of the nose are prevalent and thought to be related to this use[].

Agroforestry Uses:

It is planted to protect sand dunes and bare soil in dry areas from wind and water erosion[, ]. E. Tirucalli fences can act as erosion breaks[].
It is unsuitable for intercropping since it suppresses undergrowth, including crops[].
An effective plant for land reclamation programmes, it is very drought resistant and efficient in photosynthesis because of its unique photosynthetic physiology combining both the Crassulacean acid metabolism and the C3 pathways. During humid spells when leaves are present, this combination allows high CO2 uptake and, thus, elevated growth rates[, ].
Plantations have succeeded in some instances at more than 5,000 ppm in arsenic mine spoil mounds[].
An extensively used hedge plant in rural areas of East Africa[]. Its dense growth and caustic, irritant sap combine to make an effective deterrent to small animals and human marauders from forcing a passage[, ]. The latex must also protect it from browsing animals though sheep and the omnivorous goat are said to eat it in some areas[]. The hedge can be easily established with cuttings planted in situ[].

Other Uses

A potential biomass crop[]. Its use as a source of hydrocarbons has been investigated by a number of authors, the latex hydrocarbon is largely a C30 triterpenoid which on cracking yields high octane gasoline. It is estimated that 1-2 t of crude oil can be obtained per ha per year from E. Tirucalli. The gross energy value of E. Tirucalli biomass is 17 600 kJ/kg. The biomass can be converted into gas, liquid fuels and solid fuels such as pellets, briquettes and charcoal[].

The sap evidently has strong fixative power: mixed with animal hair it is used for fastening knife-blades to wood handles and spear-heads to shafts[, , ].

The latex is piscicidal and insecticidal[]. It showed strong activity against Colletotrichum capsici, Fusarium pallidoroseum, Botryodiplodia theobromae, Alternaria alternata, Penicillium citrinum, Phomopsis caricae-papayae and Aspergillus niger[]. The latex is highly toxic to the parasitic nematodes. Hoplolaimus indicus, Helicotylenchus indicus and Tylenchus filiformis[].
The plant is also used as an effective repellent for mosquitoes and ants[, ].

The latex is an emulsion of about 30% (principally euphol) terpenes in water. During the Second World War the latex was used in South Africa in the development of a rubber substitute, but this proved to be unstable and unprofitable due to the high latex resin content[, ].
Euphorbia latex contains a mixture of light hydrocarbons of molecular weight around 20,000, and after removal of the water the residue is a liquid oil[]. Triterpenic alcohols have also been identified in the latex[]. A form of rubber is obtained from the latex which contains a high proportion of resin: 14.3 - 15.7% caoutchouc, 75.8 - 82.1% resin, dry weight, in material from S Africa. The resin can be used in varnishes for certain purposes in the absence of better materials, but only at a high cost[]. Steam-distillation results in a better product which has found some favour in India in linseed-oil varnishes giving a tack-free glossy finish[].

An oil obtained from the latex was formerly used in linoleum, oilskin, and leather cloth industries[].

Methane can be produced by anaerobic fermentation of the latex[].

The wood is white, close grained and fairly hard. It is rarely attacked by insects. It is used for toys, rafters and veneers[, , ].
The wood is used for fuel when better options are unavailable, and it gives a charcoal suitable for gun-powder, and for the manufacture of fireworks[, , ].

Propagation

Seed -
Cuttings root easily. Cut fresh branches from a healthy bush. Cuttings should be at least 10cm long, and should be left to dry for at least 24 hours before planting. For ornamental purposes, cuttings of 35 - 40cm long are usually taken and for hedges cuttings of up to 1 metre long can be used[]. Take care to avoid direct contact with the milky sap, which can cause skin irritation. Plant at the onset of the rainy season in shallow trenches about 20 cm deep where water can collect[].

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