Purslane (Portulaca oleracea) is a low, sprawling succulent eaten as a leafy green for its small, plump, paddle-shaped leaves, its smooth reddish stems and its bright, lemony-sour and faintly salty-mineral bite. The crisp, juicy leaf has a cool, slightly mucilaginous flesh that thickens whatever it touches, and it is the richest leafy-green source of omega-3 fatty acids. Dismissed by gardeners across the world as a weed, it is in fact a long-cultivated vegetable — eaten raw in Levantine fattoush, Mexican verdolagas and Greek glistrida, and lightly cooked into stews and stir-fries.