Aloe gerstneri Reynolds, 1937

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

E Aloe gerstneri Reynolds

Common names.

Gerstner’s aloe (English); bergaalwyn (Afrikaans); isihlabane (Zulu).

Description.

Acaulescent plants or stem short; rosettes solitary, erect, 0.4-0.7 m high. Leaves densely rosulate, arcuate-erect, dull grey-green, without spots, texture smooth, lanceolate-ensiform, 40-60 cm long, 6-12 cm wide at base, lower surface sometimes with few spines in median line near apex (can be copiously spiny on both surfaces in young plants); margin not distinctly coloured, with isolated, pungent, deltoid, pale brown teeth from white sub-tuberculate base, 4 mm long, 10-15 mm apart; exudate honey-coloured. Inflorescence 1.0-1.3 m high, erect, simple in young plants, 1- to 3-branched from below middle in mature plants. Racemes cylindrical, slightly acuminate, up to 36 cm long, 6-7 cm wide, very dense; buds and flowers pendent. Floral bracts 18 mm long, 5 mm wide. Pedicels 5 mm long. Flowers: perianth reddish-orange in bud, flowers yellowish-orange, 24-30 mm long, ± 7 mm across ovary, narrowing slightly towards mouth, cylindrical-ventricose, slightly clavate, mouth slightly upturned; outer segments free for 15-17 mm; stamens exserted to 13 mm; style exserted to 14 mm.

Flowering time.

February-March.

Habitat.

Rocky slopes in grassland in areas with cold winters and reasonably high rainfall, on granite or quartzite formations.

Diagnostic characters.

Aloe gerstneri can be distinguished from other virtually acaulescent, non-maculate aloes in KwaZulu-Natal ( Aristaloe aristata , Aloe chabaudii var. chabaudii , Aloe pratensis , Aloe reitzii var. vernalis , Aloe suprafoliata and Aloe vanbalenii ) by the very dense racemes (up to 36 × 6-7 cm) with short erect pedicels (5 mm). Flowers are yellowish-orange, 24-30 mm long, tubular and straight, pointing downwards and almost pressed against the stalk, with conspicuously exserted stamens and style. Leaves can be copiously spiny on both surfaces in young plants, but mature leaves (40-60 × 6-12 cm) are without surface prickles (sometimes with spines on median line of lower surface), arcuate erect, dull grey-green and with pungent marginal teeth on a distinctive white base.

Conservation status.

Endangered. Threats include habitat degradation owing to erosion caused by overgrazing and subsistence farming ( Raimondo et al. 2009, L. von Staden pers. comm.).

Distribution.

Restricted to a small area in northern KwaZulu-Natal, South Africa (Fig. 15 ).

Figures

Figure 15. Aloe gerstneri. Photo: E. van Wyk.