Increasing the planting density of Cryptolepis sanguinolenta (Lindl.) Schlt increased root biomass and cryptolepine yield

Cryptolepis sanguinolenta (Lindl.) Schlt. is an important multipurpose medicinal plant used for the treatment of ailments such as malaria. Despite the ongoing efforts in domesticating the herb, the ideal planting density and its benefits are unknown. A study was conducted to determine the influence of six C. sanguinolenta accessions and three planting densities (15, 30 and 45 plants/1.8 m2) on root biomass, cryptolepine concentration and cryptolepine yield. Also, benefit-cost ratios were determined for each plant density across the four cultivation periods (9, 12, 15 and 18 months). The cultivation of C. sanguinolenta at the highest planting density (45 plants/1.8 m2) increased root biomass (value), cryptolepine content (2.08 mg/100 mg dry root) and cryptolepine yield (23.31 mg mg/1.8 m2) compared to those cultivated at lower planting densities (15 and 30 plants/1.8 m2). The duration for growing C. sanguinolenta had a more significant influence on cryptolepine yield but not the cryptolepine content. Plants cultivated for 15 months gave the maximum cryptolepine yield (10.33 g/bed), indicating 15 months as the optimum time to harvest the roots. The benefit-cost analysis revealed that growing the plant at a density of 45 plants/1.8 m2 (25,920 plants/acre) for 18 months was a more profitable venture with a benefit-cost ratio of 3.45. Commercial cultivation of C. sanguinolenta at 45 plants per bed area of 1.8 m2 (25,920 plants/acre) for 15–18 months is recommended as the most profitable and promising cropping practice to ensure the sustainable supply of planting material.