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Accepted Scientific Name: Euphorbia olowaluana Sherff
Bot. Gaz. 97: 580 (1936)
Origin and Habitat: Endemic of the Abd al Kuri Island, next to Socotra Island, Yemen.
Habitat: It grows only in one locality on the Quatar Saleh (or Jebel Hassala) in a very arid area at an elevation of about 150 to 270 m in the middle of the mountain on limestone outcrops and granitic gravel slopes where they forms open thickets. The species is severely endangered and was reduced to only four clumps in 1967. The reasons for its decline are obscure: livestock do not touch it since it is highly poisonous. In the past this species was much more abundant all over a ridge from about 150 to 450 metres. Abd al Kuri is semi-desert with little or no vegetation.
Euphorbia olowaluana Sherff
Bot. Gaz. 97: 580 (1936)
- Euphorbia olowaluana Sherff
- Euphorbia olowaluana var. gracilis (Rock) Sherff
- Euphorbia olowaluana var. lepidofolia O.Deg. & Sherff
Description: Euphorbia abdelkuri is a very peculiar candelabra-like succulent plant lacking both leaves and spines, which looks like a grey candle with whitish-grey melted wax on it. It form densely branched candelabra-like clumps usually not more than 1 m hight by 1.5 in diameter on one clump (but occasionally in habitat some plants can reach 3 m of height and an equivalent diameter). It is one of the most coveted Euphorbia species.
Remarks: It is the only Euphorbia species with yellow a yellow sap.
Stems: About 5 cm in diameter, pale greenish-grey, ash-grey to tan, columnar, more or less cylindrical, slightly constricted at intervals, spineless, simple, branching from the base or occasionally splitting dichotomously. Generally has 6 ribs with a somewhat wrinkled, worn looking 'skin' with slightly raised conical tubercles. Often skin peels away revealing greener tissues beneath. The colour of the new growth is grey-pink to dark brown and it will then turn to the grey tan colour. The latex is yellow viciously acrid and highly poisonous.
Leaves: Very small, ephemeral.
Inflorescence: Simple cymes, very contracted from the base of the tubercles born towards the top of the stems.
Flower (cyathia): Small, turbinate, about 5 mm in diameter on 8 mm long peduncles. Nectar glands yellowish. Pedicel very short.
Fruit: Trigynous, vaguely lobed, dull-green, about 8 mm in diameter.
Bibliography: Major references and further lectures
1) Balfour, I. B. "Angiospermae" in Forbes, H. O. (ed.), "The natural history of Sokotra & Abd-el-Kuri" The Free Public Museum, Liverpool pp. 528-530 1903
2) James Cullen, Sabina G. Knees, H. Suzanne Cubey “The European Garden Flora Flowering Plants: A Manual for the Identification of Plants Cultivated in Europe, Both Out-of-Doors and Under Glass” Cambridge University Press, 11/ago/2011
3) Lavranos, J.J. "The island of Abd al Kuri and its peculiar Euphorbia." in: Cact. Succ. J. Amer. 43: 109-111 1971
4) Gren Lucas "The IUCN Plant Red Data Book: Comprising Red Data Sheets on 250 Selected Plants Threatened on a World Scale" IUCN, 01/gen/1978
5) Urs Eggli “Illustrated Handbook of Succulent Plants: Dicotyledons” Springer, 2002
6) Volker Buddensiek "Sukkulente Euphorbien." Ulmer, 1998
Cultivation and Propagation: Due to its slow growth rate and rarity it is thought difficult to grow on its own roots. It is almost always grafted Euphorbia canariensis, but it may be degrafted and rootted and, surprisingly, it's quite easy to grow. It's uncommon to lose a plant. It like a sunny position. It does best in a mineral soil, good drainage is essential. Water sparingly during the summer months and keep dry in winter. It is a slow growing long lived plant and once established, it will be content in its position and with its soil for years. It can tolerate moderate shade, and a plant that has been growing in shade should be slowly hardened off before placing it in full sun as the plant will be severely scorched if moved too suddenly from shade into sun. Seems to have no problems growing in a heavy summer rainfall area, in extremely well drained, mineralized soil mix.
Frost tolerance: Very frost tender needs minimum winter temperatures around 10° C (or even more)
Propagation: It is usually reproduced by grafting or cuttings, but it may be propagated from seed sown during spring or summer (seeds are seldom available).
Grafting: The plants that are grafted on a more vigorous and easier stocks are easier to keep, grow faster and produce more flowers and seeds. The method of grafting euphorbias differs little from that of other succulents, except in one important aspect. The latex must be washed or sprayed off until hardly anything remains. After the latex flow has stopped, a further 1-2 mm slice can be taken from both surfaces without a new latex flow starting. Both scion and stock need to be at the start of the growing season. The stock should be cut as near as possible to the growing tip, as here the vascular bundles are dense and not yet woody and will feed the scion in the best possible way. Where possible stock and scion should be of similar diameter. The cut surfaces are held together with elastic bands in cross style, over the plant top and under the pot. The plants should be left in an airy and shady place for 7-10 days before the bands are removed. E. abdelkuri is grown almost exclusively grafted on Euphorbia canariensis which proven to be the ideal grafting stock. The grafting are very successful, new grafts often show growth within 3 weeks.
Warning: As with all other Euphorbias when a plant get damaged it exudes a thick milky sap known as latex. This latex is poisonous and particularly dangerous for the eyes, skin and mucous membranes. So pay extreme attention not to get any in your eyes or mouth. Cultivated plants must be handled carefully.
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