The Enon Conglomerate cliff substrate is mineral-poor, giving rise to slightly acidic soil. The crevices and ledges, perhaps not as efficient as crevices and ledges on sandstone or dolomite, provide habitat for a few endemic cliff-dwellers, such as this obligatory cliff-dwelling Enon form of Haworthiopsis attentuata var. attenutata. The poor soil and harsh cliff habitat cause stress that results in plants that are adapted to this particular environment.

Haworthiopsis attenuata ‘Enon’ plants in habitat are very variable in leaf epidermis colour and shape. This genetic variability is the basis for adaptation and shows a healthy, genetically variable population. The plants vary in the tubercle size, shape and colour as well as general leaf shape.

Fig. 7. A close-up of the leaf texture of an Enon haworthiopsis growing in a container.

The plants grow in conspicuous, compact, mat-forming to globose clusters. The succulent leaves provide sufficient moisture, enabling the plant to cope with regular dry periods. The leaf orientation is ascending to spreading becoming somewhat recurved to maximise absorption of light on the shady south-facing cliff. The green leaves become reddish during dry conditions, as a result of the pigment anthocyanin, reducing photosynthesis. The plants are also slow-growing and long-lived, with firm leaves withering from the base. The fleshy leaves becoming turgid after rain, and are channelled during dry periods, an adaptation to the dry habitat. The slow growth rate and long-lived leaves can be viewed as an adaptation to mineral-poor soil. The leaves of this Enon form of Haworthiopsis attenuata are more triangular and shorter, with a reduction in tubercles and often with a smooth surface, all adaptations to the shady, south-facing cliff environment.

Fig. 8. A dense mat-forming group of two clones of Haworthiopsis attenuata ‘Enon’ on a ledge on a south-facing Enon Conglomerate cliff at Enon near Kirkwood, Eastern Cape.

The inflorescence is ascending to spreading, the small, tubular, 2-lipped, white corolla attracting a pollinating flying insect. The seed is small and angular, ideal for establishment in crevices. The light seeds are shaken from the capsules and dispersed by wind. The seeds ripen in summer and autumn, coinciding with the rainy season. Germination occurs after about 14–21 days.

Haworthiopsis attenuata ‘Enon’ is very prolific and suckers freely from the base, forming dense clusters. The different clones on the cliff face are easily distinguishable. Continual sprouting from the base represents an efficient vegetative backup dispersal strategy for this harsh cliff-face environment.