Bitterleaf is the foliage of Vernonia amygdalina, a small tropical African shrub whose leaves are, as the name promises, intensely bitter. Washed and hand-squeezed to draw out most of that bitterness, they are the signature green of West African soups such as onugbu and bitterleaf soup, and are cooked alongside egusi and other stews across Nigeria, Cameroon and the wider region.