This species was discovered in 1960 on the lower slopes (700–1200 m.) of Mt. Kasigau in southern Kenya, where it grows on exposed rock faces. It has not been recorded from other places since then.
Although at first sight it reminds one of a multi-angled E. heterochroma, it has some distinguishing features: usually not higher than 1 m, branches always rigid and uniform sap-green.
The plants do very well in cultivation and can easily be propagated from cuttings.
It is a shrub with more or less erect branches which are sparsely rebranched, prominently 6–9-angled, 1–3 cm. thick and bright green; the angles are shallowly toothed, with teeth 6–12 mm. apart.
The grey spines are to 8 mm. long; without or with rudimentary prickles
Cyathia are ± 3 × 4 mm., with cup-shaped involucres; the golden yellow glands are transversely oblong, ± 1 × 2 mm. and the lobes are subcircular, ± 1.3 × 1.3 mm.
The capsules are obtusely 3-lobed and exserted on a reflexed pedicel to 4 mm. long.
Even though this is not the most imposing of the tree Euphorbias, a mature specimen is a sight for sore eyes, especially when it is decorated with its big bright red fruits.
When fully developed, the trees may be 9-10 m tall, with a short bulky trunk and a dense crown of upcurved stems. The tips of the branches are usually 4- angled, 4 to 6 cm wide, and regularly constricted into oval segments to 15 cm long; the angles are straight to shallowly waved.
The spine shields are triangular, to 1 x 0.7 cm; they are separate and become corky with age. The spine pairs are up to 0.5 cm long, often not completely developed or apparently absent.
The cyathia are 1.2 cm across, with golden yellow glands; the fleshy
fruits are about 1.5 x 2 cm, first white, then turning bright red, and hardening over time.
Euphorbia abyssinica occurs at altitudes between 840 and 1460 m in Sudan (Red Sea Hills), Eritrea, N. Ethiopia, Somaliland, and N. Somalia, on dry stony slopes and bushy savannahs, sometimes growing on its own but often locally dominant.
The stem is used for firewood and as timber and the sap is sometimes used in traditional medicine and to kill ticks on cattle.
In suitable climates, the species is grown as an ornamental house plant and also as a garden plant. It is best propagated by seed because cuttings do not develop the characteristic trunk.
Name Euphorbia grandicornis is a representative of the large group within the genus of shrub-like succulents with spine pairs, also referred to as the diacanthium section. Plants belonging to this group usually have 2 spines that are facing outwards from the edge of a shield. Another example of a member of this group is E. canariensis. Sometimes there are 3 or 4 spines and sometimes only one (for example, in E. unispina).
Grandicornis literally means ‘with large horns’.
In English-speaking countries, the plant is also called ‘Cow’s horn Euphorbia’. The thorns remind me more of the tentacles of a snail. See Fig. 1.
In the next image, we see (between the spines) the scars of the tiny leaves that are formed in the new growth and that will soon turn yellow, shrivel, and fall off.
Other names that are widely used are ‘Big horned Euphorbia’, ‘Rhino thorn’ and even ‘Zig-Zag Cactus’. There is also a cristate form and this looks even much more ferocious than the normal plant. In Afrikaans, the plant is called renosterdoring (a renoster is a rhinoceros and doring stands for thorn).
History The plant has probably been in cultivation for quite a long time, but for many years it went undescribed.
We first come across the name Euphorbia grandicornis in 1889 in the first part of the 2-volume book ‘Pflanzenbiologische Schilderungen’ by the German professor of botany dr. Karl Immanuel Eberhard Ritter von Goebel. In a general story about Euphorbias, he discusses a number of aspects of E. grandicornis as if it were a well-known plant. It is nothing like what we mean by a description nowadays. However, we do find a beautiful pen drawing of a top cutting (Fig. 3).
In addition, there is a drawing of the leaves in the new growth and of a cross-section of the trunk in which the peculiar, twisted shape of the winged ribs is clearly illustrated (Fig. 4).
Von Goebel reports that he has not been able to find any data on the habitat. However, from the physical appearance of the plant with the wide thin ribs and therefore a large surface area – similar to, for example, leaf cacti- he concludes that it is unlikely to be exposed to long dry periods in its natural environment.
After von Goebel it was quiet until 1893. In that year, an article by a Mr. J.E. Weiss, Reader in botany, appeared in the periodical ‘Dr. Neubert’s Deutsches Garten-Magazin’ under the title “Empfehlenswerte Cacteen” (“recommendable cacti”). He took the concept of cactus rather broadly because the last ‘cactus’ discussed in his article is Euphorbia grandicornis. There is even a photo, the very first one published, but the print quality was rather poor in those days (Fig. 5).
Original description The plant was still not officially described at the time. That was done in 1897 by Nicholas Edward Brown in part 26 of Hooker’s Icones Plantarum. That is why the author’s citation which is always added to the species name in scientific literature, in this case is ‘Goebel ex N.E. Br.’. The description by Brown, who was employed by Kew Gardens near London, was based on a plant that had been cultivated there since 1876. The description with Latin diagnosis was accompanied by two drawings of quite a big specimen. I don’t particularly like these drawings. Brown also mentioned a locality: South Africa, Umfolosi River, Zululand.
Habitat Nevertheless, there was apparently uncertainty as to where the plant occurred in nature, because in 1904 in Engler’s ‘Botanische Jahrbücher’ ( ‘Botanical Yearbooks’) in a monography on Euphorbia’s in the section Diacanthium the author, F. Pax, writes: “Vaterland unbekannt, vielleicht Africa” (Native country unknown, maybe Africa). And in 1907 Alwin Berger in his ‘Sukkulente Euphorbien’ says: “Homeland ?” and further down: The origin of the plant is unknown. However, it is not plausible that it was only recently introduced, because the large specimen in Kewmentioned above, indicates that it is an old inhabitant of our greenhouses.). Brown and others later compiled the part about the Euphorbiaceae in Sir William T Thiselthon-Dyer’s ‘Flora Capensis’. This part appeared in 1915 and here E. grandicornis is also treated. The last line I find quite funny: “Distribution: Easter Region: Zululand, stone! Marriott! And cultivated specimens!”. I suspect Marriott is a name, but I haven’t been able to find any information. But especially all those exclamation marks intrigue me. I have no idea what the writer wanted to emphasize with this.
In modern literature, it is made clear that the range is quite large: South Africa (Kwazulu-Natal), Swaziland, Mozambique, Kenya. There the plants grow at low altitudes (up to 400 m) in small groups between grass or shrubs. They have 3 or 4 ribs and can be up to 2 m tall. It seems that large plants often succumb to their own weight. The variety sejuncta (described in 1970 by Leach), which remains smaller and sometimes grows lying down, has 2 or 3 ribs and is known only from a site in Mozambique. There it grows in the company of Aloe chabaudii, Euphorbia corniculata and E. tirucalli on granite slopes at altitudes between 380 and 700 meters.
Flowering In a sunny location, a plant that is preparing to flower stands out because of the vivid red colour of the developing cyathia (Fig. 6).
These appear on the uppermost and therefore youngest, segments of the stems. There are always 3 cyathia together, but often only the middle one will fully develop. It only produces male flowers (stamens). The two outer cyathia are bisexual. First, the male flowers develop (Fig. 7)
and when they dry out, the female flower (pistil, fig. 8) follows.
All cyathia are bright yellow in colour. This type of inflorescence with a central male inflorescence flanked by 2 bisexual cyathia is often found in Euphorbias, for example in E. canariensis. Ripe fruits are about 8 mm in diameter and purplish-red in colour (Fig. 9).
Fruit formation in a E. grandicornis in Jan Celliers Park (Pretoria, South Africa). Photo Dr. Johann C. Knobel.
Cultivation A well-drained mixture with little organic material and a lot of additions such as lava, pumice, clay chunks, etc. is recommended. It’s best not to use peat. Give ample water from March to September. In winter, the temperature should be at least 12 °C, but preferably a little higher. Propagation is by cuttings, which root quite easily, or by sowing. Seed is fairly well available and it is fascinating to see how a wildly thorned plant develops from the delicate seedling with its 2 cotyledons (Fig. 10).
In frost-free areas, E. grandicornis is recommended for hedges. Pruning is well tolerated. Goats eat the corners off but leave the thorny sides alone. The juice doesn’t seem to hurt them.
Literature: Berger, A. (1907). Sukkulente Euphorbien: 52-53.
Brown, N.E. (1897). Hooker’s Icones Plantarum 26, plates 2531, 2532.
Brown, N.E.; Hutchinson, J.; Prain, D. (1915). Euphorbiaceae in Thiselton-Dyer, Flora Capensis 5, sect 2, part 2: 367-368.
Goebel, K. von (1889). ‘Pflanzenbiologische Schilderungen’ 1: 62-63.
Pax, F. (1905).. Monographische Übersicht über die afrikanische Arten aus der Sektion Diacanthium der Gattung Euphorbia in Engler’s Botanische Jahrbücher 34: 74.
Weiss, J.E. (1893). Dr. Neubert’s Deutsches Garten-Magazin 46: 291.
First published in Succulenta 92 (4) 2013. Translation from the Dutch by F.N.
Common names: Somali tree aloe, Daar Der (= the tall Aloe)
Of the seven Aloidendron species, only two are found outside Namibia, South Africa, and Mozambique: A. sabaeum (Arabian peninsula) and A. eminens, which at first glance is somewhat similar to the much more familiar A. barberae from South Africa.
It is an upright tree 10-15 m tall, looking somewhat untidy because of its irregularly branching. Its trunk is up to 1.5 m in diameter at ground level.
16-20 leaves are gathered at the tip of each branch; they are 40-45 cm long and about 5 cm wide at the base, gradually narrowing to an obtuse, downwards pointing tip. The upper surface is dull-green and u-shaped in cross-section, whereas the lower surface is rounded; the margins are white with blunt teeth.
The branched inflorescences are 50-60 cm high, with red, somewhat glossy flowers, which are cylindrical-trigonous on cross-section, rather thick and fleshy, and about 4 cm long. They appear mostly in November-February and are pollinated by birds.
Although the species is still locally common in northern Somaliland, it is endangered by habitat loss, logging, and wood harvesting.
It occurs in sheltered, well-wooded ravines and on steep rocky limestone slopes North of Erigavo (Ceerigabo), between about 1500 and 2000 m. The climate is relatively cool here with between 600-1000mm rain per year.
This species belongs to a small group of Ethiopian/Eritrean aloes in which the flowers are covered in fine hairs. Its rosettes have no stems or a very short one and are solitary or forming groups. Each rosette has 12-20 leaves; these are 25-70 cm long and 2.5-13.5 cm wide, more or less erect, and slightly grooved. In adult plants, the leaves are dull greyish green without spots; in young ones, they are densely pale spotted.
The inflorescences are up to 2 m high, erect with usually 2-3 branches. The flowers are cylindrical-triangular and 20-30 mm long, pale to bright pink and covered with soft, white, sometimes dense hairs -the species name refers to that fact (trich- : hairy and anthos: flower).
There are 2 subspecies, with small but consistent differences and (as far as is known) a wide gap between the distribution areas. ssp. trichosantha grows in open dry bushland between 900 and 1700 m in the northernmost region of Ethiopia, in Eritrea, and maybe also in Sudan.
Marginal teeth 8-12 per 10 cm and 4.5 -5.5 mm long; flowers 20-23 mm long, mainly present in the dry season: Febr.-May. ssp. longiflora is widespread further south in Ethiopia, where it occurs abundantly in open deciduous bushland on volcanic rocks and alluvial soils at altitudes between 1000 and 1950 m.
Marginal teeth 4-8 per 10 cm and 2-4 mm long; flowers (23-) 25-30 mm long, present almost throughout the year. The pictures below show this subspecies.
From southern Ethiopia and South Sudan to Rwanda and Tanzania, this Aloe is widely distributed on sandy stony soils in grassland and open dry woodland. Sap from the leaves is used as an eye-lotion and the roots are used in beer-making.
The plants are single or form small groups; they are usually stemless, but older plants may have a short thick stem.
There are about 20 firm leaves in a compact rosette to 1 m. in diameter; they are 30-75 cm long and 15-30 cm wide near the base with marginal teeth (usually very sharp) and sometimes a horny rim; the colour varies from glossy dull green (covered with greyish-white to bluish-green bloom in the dry season) to darker green and bronzed.
The inflorescence is 1-2 m tall with 10-20 branches; the flowers are 2.5-3.5 cm long and may be bright coral-red, dull scarlet or pink with minute white spots.
Plants belonging to this subspecies occur fairly widespread in northeast Uganda and northwest Kenya in sandy rocky soils, usually in the open at altitudes between 1075 and 1850 m.
They have a thick fleshy root with densely tufted, more or less round branches, which are 5-8 mm thick and erect to 15 cm tall or creeping to 50 (-100) cm long.
The branches bear tubercles to 2 cm apart in 4 series, with triangular spine shields 6 x 1.5 mm in size and spines 5-15 mm long; they differ considerably in colouring, from bright green often with darker longitudinal stripes to greyish-green with purplish stripes.
