Influence of resting period on fruits and secondary tubers of Harpagophytum procumbens in Namibia

Abstract

Harpagophytum procumbens, the devil’s claw, is a plant with medicinal values in Namibia, leading to high demands, and resulting in unsustainable harvesting techniques by locals. The most commonly practiced harvesting period is 2 years, mostly dictated by the need to make as much money as possible. A study was undertaken to investigate the effect of extending the current 2 year harvesting period to 5 years on secondary tuber and fruit production. Two experimental plots at two sites (Vergenoeg and Tjaka Ben Hur) were explored. The first plot had plants harvested every 2 years and another only after 5 years. Between sites and within sites differences in means were analyzed using a t-test at _ = 0.05. Results established that there was no difference in fruit production between the 2 groups at Vergenoeg (p = 0.375) and Ben Hur (p = 0.131). However, between sites variability in number of secondary tubers was Observed (p = 0.014). Particularly, at Vergenoeg, the number of secondary tubers pro duced after 5 years, were abundant (p = 0.003). In addition, the harvest at Vergenoeg showed a difference in weight of secondary tubers between the 2 groups (p = 0.006). Within Ben Hur, there was no difference (p = 0.928) between the numbers of secondary Tubers produced at 2 years and at 5 years. A holistic management approach (rotational harvesting) is recommended for to harvest every 5 years to maximize benefit and sustain the species.