56 Achieving a fair and sustainable trade in devil’s claw (Harpagophytum spp.)THE RESOURCE BASEThe ecology of devil’s claw
Devil’s claw, of the genus Harpagophytum DC. ex Meissn., in the family
Pedaliaceae, is endemic to the Kalahari region. The plant is perennial and has
a tuberous rootstock, from which prostrate annual stems spread bearing greyish-
green leaves. Its tubular flowers have a maroon to pink colour and develop
into the characteristic fruits that give the genus Harpagophytum (‘hook plant’,
when translated from the Greek) its colloquial name, devil’s claw. The fruits
have numerous long arms with sharp, hooked thorns, as well as two straight
thorns on the upper surface (Photo 1). Dispersal of the seed occurs through
entanglement of the fruit in the wool, tails or feet of animals and its subsequent
implant in sandy soils (Phillips 1938), leading some to state that the name
devil’s claw originates from the bedevilled dance that animals do to get rid of
the fruit that has run into their hooves (Moatti et al. 1983). While devil’s claw
is the name most widely associated with the plant, at least 20 other names
are used to refer to it.
Harpagophytum occurs between 15° and 30° latitude in Namibia, Botswana,
South Africa, Angola and, to a lesser extent, Zambia, Zimbabwe and Mozambique
(Ihlenfeldt and Hartmann 1970). Two species occur in southern Africa,
Harpagophytum procumbens and Harpagophytum zeyheri, which can be subdivided
into five subspecies differentiated by their fruit and leaf characteristics and
geographical distribution. While both species are accepted for medicinal use, it is
H. procumbens that is mostly traded and recognised by the international
pharmacopoeia (Blumenthal 1998). However, H. zeyheri is very similar in
appearance to H. procumbens and the two species may be easily confused.(Harpagophytum procumbens)04devilcslaw.P65 56 22/12/2004, 11:04