Forest Products, Livelihoods and Conservation

Rachel Wynberg 57

Photo 1. Devil’s claw flower with leaves (Photo by R. Wynberg)

Both species are considered in this paper because of the difficulties of

distinguishing between them, and because of an increasing trade in H. zeyheri,

but for the most part discussion is focused on H. procumbens, the species

found in the study area.

H. procumbens typically occurs in the red sandy soils of the Kalahari desert,

in areas coinciding with some of the driest parts of the region (Figure 2). To

survive the dry period the plant forms water-storing secondary root tubers

which branch off horizontally from the primary taproot, and it is these roots

that are used in phytotherapy to treat a wide variety of ailments. Varying

assessments suggest the secondary tubers can attain depths of 2 m, lengths

from 4 cm to 25 cm, and a diameter up to 6 cm (Taylor and Moss 1982; Hachfeld

1999). The growing season of the plant typically commences in December,

following sufficient rains, and ends in April-June after the plant has produced

seeds and accumulated adequate phytosynthates to facilitate growth in the

following season (Strobach 1999). Flowers and leaves of the plant are visible

only during the active growing season, when suitable climatic conditions prevail.

After rains these parts of the plant dry out rapidly and soon disappear, making

location of the tubers extremely difficult. Both the abundance and visibility

of the plant are strongly correlated to rainfall.

H. procumbens is considered a ‘common weed’ (Phillips 1938; Henderson

and Anderson 1966) and is frequently reported to be more abundant in

disturbed, trampled or overgrazed areas including road verges, firebreaks

and dune slopes (Ihlendfeldt and Hartmann 1970; Nott 1986; Hachfeld 1999).

Nott (1986) attributes this to the deep root systems of H. procumbens and the

inability of the plant to compete with the shallow root systems of grasses.

Because grasses use topsoil water, moisture penetration to the subsoil is

reduced, as is the ability to sustain the deeper root systems of H. procumbens.

Indeed, several authors note that the plant occurs in greater numbers where

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