By Philip Newell
Senna obtusifolia (or Cassia obtusifolia) is a hardy and indigenous leafy vegetable (ILV) that grows in the Sahel. To better understand it, The International Crops Research Institute for Semi-Arid Africa (ICRISAT) studied the plant to determine the best planting density and preparation techniques, as well as its potential cultivation among Acacia trees.
ICRISAT’s research found that this protein-rich vegetable, which is used as a meat substitute, grows well at a high density. Using three different planting densities (.5x.5m, .5 x 1m and 1x1m), they found that the highest density resulted in the highest per-acre harvest weight – meaning that it is not highly competitive for water or nutrients. Generally the plant is grown by women around the edges of maize or millet fields. According to ICRISAT, concentrated, intentional planting can result in a significant harvest during the “hunger period.” This period is the months, generally June-October, when farmers have exhausted their store of grain and money, leading to the threat of starvation.
While it is common to collect wild Senna obtusifolia during the hunger period, the cultivation of this crop is not widespread. The leafy quality of the plant means that harvests can be small and ongoing, leaving the plant to continually grow new leaves. While women may sow this crop along the edges of the field or in other marginal land, the scaling up of production is seen as a potential way to increase food security at a low cost.
The study also looked into the nutritional effects of the traditional cooking method for Senna obtusifolia. They found that the traditional three-hour boil serves to not only reduce the pungent odor of the leaves, but also increased the concentration of lignin and did not adversely affect the other nutrient concentrations.