Aloe marlothii A.Berger, 1905

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 marlothii A.Berger

Common names.

Mountain aloe (English); bergaalwyn, boomaalwyn, snuifaalwyn (Afrikaans); ikhala, imihlaba, inhlaba, inhlabane, umhlaba (Zulu).

Description.

Solitary, arborescent plant of up to 5-6 m high (subsp. marlothii ) or 1.00-1.75 m high (subsp. orientalis ). Stem simple and erect (subsp. marlothii ) or often suckering to form small groups and erect or oblique to procumbent (subsp. orientalis ), densely covered with persistent dried leaves. Leaves densely rosulate, suberect to spreading and eventually pendent, dull grey-green to glaucous (subsp. marlothii ) or arcuate-incurved to spreading or slightly decurved, glaucous to blue-green (subsp. orientalis ), without spots, with scattered, reddish-brown, pungent spines, usually more copious on lower surface (subsp. marlothii ) or with no to few surface prickles (subsp. orientalis ), lanceolate-attenuate, 100-150 cm long, 20-25 cm wide at base (subsp. marlothii ) or 75-150 cm long, 8-25 cm wide at base (subsp. orientalis ); margin with stout, pungent, reddish-brown teeth, 3-6 mm long, 10-20 mm apart (subsp. marlothii ) or 3-4 mm long, 8-25 mm apart (subsp. orientalis ); exudate honey-coloured. Inflorescence up to 0.8 m high, 10- to 30-branched from below middle, lower branches rebranched, branches horizontal to spreading. Racemes cylindrical, 30-50 cm long, horizontal to suboblique (subsp. marlothii ) or 15-25 cm long, spreading to rarely erect (subsp. orientalis ), dense; flowers markedly secund when open. Floral bracts 8-9 mm long, 5 mm wide (subsp. marlothii ) or 4-9 mm long, 2-5 mm wide (subsp. orientalis ). Pedicels 5-8 mm (subsp. marlothii ) or 3-5 mm (subsp. orientalis ) long. Flowers: perianth orange to yellowish-orange, 30-35 mm long, ± 7 mm wide across ovary (subsp. marlothii ) or yellow to orange, 18-30 mm long (subsp. orientalis ), enlarging above ovary, narrowing towards usually wide-open mouth, cylindrical-clavate to cylindrical-ventricose (subsp. marlothii ) or cylindrical to ventricose (subsp. orientalis ); outer segments free for 20-23 mm (subsp. marlothii ) or for 6-15 mm (subsp. orientalis ); stamens exserted to 15 mm; style exserted 15-20 mm (subsp. marlothii ) or stamens and style exserted 8-12 mm (subsp. orientalis ).

Flowering time.

June-August, as late as September along the Witwatersrand, Gauteng, South Africa (subsp. marlothii ). July-August (subsp. orientalis ).

Habitat.

Aloe marlothii subsp. marlothii grows in a wide variety of habitats, including bushveld on stony, usually bare soils or rocky outcrops. Aloe marlothii subsp. orientalis is confined to coastal grassland in sandy soil.

Diagnostic characters.

Aloe marlothii differs from the other tall often single-stemmed aloes in KwaZulu-Natal with branched inflorescences and persistent dried leaves ( Aloe candelabrum , Aloe pluridens , Aloe rupestris , Aloe spectabilis and Aloe thraskii ), by having its racemes horizontal to oblique (not erect) with the flowers secund. The inflorescence is much-branched with up to 30 racemes. Flowers are yellow to orange, up to 35 mm long with the inner segment tips purplish and the exserted portion of stamens deep purple (not deep purplish-black to black segment tips and orange filaments as in Aloe spectabilis ). Aloe marlothii subsp. marlothii is further distinguished by the presence of copious spines on both leaf surfaces. The main characters separating Aloe marlothii subsp. orientalis Glen & D.S.Hardy from the typical subspecies is its short stems of up to 1.75 m (not up to 4 m), that are sometimes oblique or procumbent and often suckering to form clumps (not solitary rosettes). Its leaves also have no or only a few surface prickles, while its racemes are usually oblique (not as horizontal as in subsp. marlothii ). Drying leaves of Aloe marlothii subsp. orientalis have a peculiar, unpleasant odour ( Glen and Hardy 1987).

Conservation status.

Both subspecies are Least Concern ( Raimondo et al. 2009).

Distribution. Aloe marlothii subsp. marlothii (red on map) is widespread throughout North-West, Limpopo (as far north as the Soutpansberg), Mpumalanga, Gauteng and KwaZulu-Natal in South Africa, as well as in south-eastern Botswana and into western Eswatini. Aloe marlothii subsp. orientalis (orange on map) is only known from northern KwaZulu-Natal in South Africa, as well as southern Mozambique and low lying areas of Eswatini (Fig. 22 ). It is near-endemic to the Maputaland Centre of Endemism.

Notes.

Aloe marlothii grades through intermediates into Aloe spectabilis Reynolds at some localities ( Reynolds 1950). As a result, the two species are considered conspecific by some authors ( Glen and Hardy 2000; Carter et al. 2011).

Figures

Figure 22. Aloe marlothii subsp. marlothii (red on map) and Aloe marlothii subsp. orientalis (orange on map). Photos: G. F. Smith (subsp. marlothii), N. R. Crouch (subsp. orientalis).