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Tropical East Africa (Kenya, Tanzania and Uganda) is a centre of diversity for spiny euphorbias with just under 90 species being recorded for the region (Carter & R.-Smith, 1988). Of these, Euphorbia baioensis is one of the most distinct and is readily available in cultivation.

This species was first discovered by Gilfrid Powys and Jasper Evans on the isolated Baio Mountain in the Northern Frontier Province of Kenya in January 1976. It was named subsequently by Susan Carter (1982) after this location. For a long time the Baio Mountain, the summit of which is 1750m, was its only known locality. It was revisited by Len Newton (1991) when he found this Euphorbia on a rocky ‘beak’ that protrudes from the southeast side of the ridge near the summit. Newton observed that the drop of about 1140m is possibly the longest vertical drop in Kenya! On the ‘beak’ the Euphorbia grows in pockets of soil amongst grass. In habitat the plant forms sprawling prostrate clumps. The stems form adventitious roots as they spread and new upright branches form along them. 

Newton was intrigued by the fact that this species had only been recorded from a single mountain. So, together with Gilfrid Powys, the original discoverer of the species, he set out to search for it on other similar mountains. They considered Holilugum Nder and Illim most likely candidates, both to the east of Baio but somewhat smaller (Newton & Powys, 1996). Both these mountains were botanically unexplored. The expedition was successful with E. baioensis being found on Holilugum Nder but not on Illim. There were many clumps of the Euphorbia, one up to 1m across. They were rooted into soil pockets and cracks in the rock and very dry. There was no evidence of regeneration. Therefore this species is currently recorded on just two mountains in northern Kenya, so it is still correct to say that this species has a very localised distribution.

02 19 FigE baioensis

 Euphorbia baioensis in a 14cm diameter pot

In contrast to its rarity in habitat, E. baioiensis is now reasonably common in cultivation, having been propagated from the original Powys and Evans collection (Powys & Evans 76/16) and distributed as Bally 16965 or Lavranos 12532. A second clone (Newton 3195) from Baio Mountain has also been propagated, so there are at least two clones now available. In cultivation the growth form is somewhat different to that found in habitat. In a pot the plant forms an upright (not sprawling) shrub with stems to 30 cm long, 2 cm diameter at the base. Branching is mainly from the base forming a dense mass. Each stem has 8 to 10 angles with spine shields bearing paired spines up to 1 cm long, grey, reddish-tipped when young becoming blackish as they age, giving the overall impression of a very bristly tight clump. My plant has yet to flower, but when produced these are a pale yellow.

Overall, Euphorbia baioensis is a very distinct species, not easily confused with any others and has no obvious close allies (Carter, 1982). This unique species is highly recommended and presents few problems in cultivation. It is readily propagated from stem cuttings.

Colin C Walker

References

Carter, S. (1982) Euphorbia baioensis. New succulent spiny Euphorbias from East Africa. Hook. Icon. Plant., 39 (3): t.3870.

Carter, S. & R.-Smith, A. (1988) Euphorbiaceae (Part 2), in R.M. Polhill (ed.) Flora of Tropical East Africa. A.A. Balkema, Rotterdam.

Newton, L.E. (1991) Euphorbia baioensis in its natural habitat. Euphorbia J., 7: 36-41. 

Newton, L. & Powys, G. (1996) In search of new localities of Euphorbia baioensis. Euphorbia J., 10: 134-141.

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