Aloe jacksonii was named in 1955 by Gilbert W. Reynolds for Major T.H.E. Jackson, who discovered it at El Kerré in the Ogaden Province of Ethiopia in 1943 whilst stationed there during the Second World War. Major Jackson wrote that “El Kerré is a strange rock outcrop with precipitous sides, and the station was built below the precipice. There is a steep path winding up a cleft, and the aloes were found along the edge at the top” (Reynolds, 1955).
There are now, however, significant questions regarding the natural habitat of this species. When the Italian Maurizio Dioli revisited El Kerré in 2000, he was unable to locate A. jacksonii despite extensive searching, following the precise information supplied to Reynolds by Major Jackson. Instead, and somewhat remarkably, Dioli found another species which was later described in 2007 as Aloe elkerriana (Dioli & McCoy, 2007). There are, therefore, mysteries surrounding these plants. Firstly, it is strange that Major Jackson did not find A. elkerriana back in 1943 because it is apparently quite common at El Kerré (Carter et al., 2011). Secondly, the origin of A. jacksonii is now uncertain: did it ever grow at El Kerré, has it died out from that location, or did Major Jackson incorrectly report its type locality? Whichever of these possibilities turns out to be correct, this species is currently only known from cultivated material derived from the original Jackson collection, hence presumably there is only a single known clone in cultivation and all plants are therefore genetically identical.
Aloe jacksonii is a very attractive, dwarf-growing species. It has short, erect or procumbent stems up to 20cm long which branch freely from the base forming clumps (Fig.1) that can be up to 50cm or more across. Its leaves are spotted, narrowly tapering with a rough spotted surface and short teeth on the margins (Fig. 2).
In my experience A. jacksonii flowers freely even as a small plant, making it highly desirable in cultivation where space is at a premium. Its inflorescence is unbranched up to 30cm tall, bearing deep coral pink flowers that are white-tipped at the mouth and up to 27mm long (Fig. 3).
As currently understood, both A. jacksonii and A. elkerriana are narrow Ethiopian endemics and, although they apparently come from the same locality, they are not closely related. Aloe elkerriana is a much larger growing and more vigorous plant than A. jacksonii with pendent or sprawling stems up to 5m long. Its inflorescence is also much larger up to 50cm tall and well-branched. Both these species have similar ecology because they are both cremnophytes: plants that grow solely on cliffs.
Colin C. Walker
References
Carter, S., Lavranos, J.J., Newton, L.E. & Walker, C.C. (2011). Aloes – The definitive guide. Kew Publishing, Royal Botanic Gardens, Kew/British Cactus & Succulent Society.
Dioli, M. & McCoy, T. (2007). Aloe elkerriana (Asphodelaceae), a new Ethiopian species from the type locality of A. jacksonii. Haseltonia 13: 34–37.
Reynolds, G.W. (1955) A new Aloe from Ethiopia. J. So. Afr. Bot., 21: 59-61, pl. X.
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