Aloe arborescens Mill. (including A. arborescens subsp. mzimnyati Van Jaarsv. & A.E.van Wyk)

Klopper, Ronell R., Crouch, Neil R., Smith, Gideon F. & van Wyk, Abraham E., 2020, A synoptic review of the aloes (Asphodelaceae, Alooideae) of KwaZulu-Natal, an ecologically diverse province in eastern South Africa, PhytoKeys 142, pp. 1-88 : 1

Aloe arborescens Mill. (including A. arborescens subsp. mzimnyati Van Jaarsv. & A.E.van Wyk)

Common names.

Krantz aloe (English); kransaalwyn (Afrikaans); inhlaba-encane, inhlazi, inkalane, inkalane-encane, umhlabana (Zulu).

Description.

Much-branched shrub, 2-5 m high. Stems erect, with persistent dried leaves. Leaves densely rosulate at branch apices, spreading-recurved, dull green to grey-green, tinged reddish in dry conditions, without spots, texture smooth, lanceolate-attenuate, 40-60 cm long, 5-7 cm wide at base; margin with firm, pale teeth, 3-5 mm long, 5-20 mm apart at mid-leaf; exudate pale yellow. Inflorescences 0.6-0.8 m high, erect, usually simple, occasionally with 1 or 2 short branches. Racemes conical to conical-cylindrical, 20-30 cm long, dense. Floral bracts 15-20 mm long, 10-12 mm wide. Pedicels 35-40 mm long. Flowers: perianth scarlet, often pink turning yellow at anthesis or occasionally yellow, ± 40 mm long, 7 mm across ovary, narrowed above ovary, widening to middle, narrowing slightly towards mouth, cylindrical-trigonous; outer segments free to base; stamens and style exserted to 5 mm.

Flowering time.

(February) June-July (August).

Habitat.

Usually in pockets of rich soil on krantz edges, rocky slopes and outcrops in areas of high summer rainfall, sometimes in dense bush.

Diagnostic characters.

Aloe arborescens is a much-branched shrub up to 5 m high, with stems rather robust (not thin and slender as in Aloiampelos tenuior ) and leaves in dense rosettes at the branch apices. Leaves are greyish-green with pale yellow teeth. Inflorescences are usually simple with elongated conical racemes that are densely flowered. Floral bracts are large (15-20 mm long) with the pedicels twice as long (35-40 mm).

Conservation status.

Least Concern ( Raimondo et al. 2009).

Distribution.

The krantz aloe is very widely distributed in south-eastern Africa and has the third widest distribution range of all Aloe species. It occurs from the Cape Peninsula (where it has arguably become naturalised), along the south and east coast of South Africa, through the Western Cape, Eastern Cape and KwaZulu-Natal and inland to Mpumalanga and Limpopo, just entering the eastern Free State, as well as further north to Mozambique and the eastern mountains of Zimbabwe and Malawi (Fig. 6 ). A robust form of the species has become naturalised along the European Mediterranean coast (see, for example, Smith and Figueiredo 2009).

Notes.

In the past, several variations of A. arborescens have been afforded formal status at subspecific or varietal ranks, the most recent being A. arborescens subsp. mzimnyati Van Jaarsv. & A.E.van Wyk, which is endemic to the lower Mzimnyati River (Buffalo River) in KwaZulu-Natal. This subspecies is distinguished by its smaller growth habit (forming a shrub of 0.50-0.75 m high), its smaller, slightly clavate flowers (22-25 mm long) that vary in colour (orange-red to orange to yellow) within the same population and its slightly later flowering time (July-August) ( Van Jaarsveld and Van Wyk 2005). We here follow the view of Smith et al. (2012), who concluded that it is better to regard A. arborescens as a single variable species, pending further research and, therefore, include A. arborescens subsp. mzimnyati in the synonymy of the species.

Figures

Figure 6. Aloe arborescens. Photo: G. Nichols.