Self-sowed can be defined as something that has grown, developed, or arisen naturally without human intervention. Its antonyms can be "cultivated," "planted," "man-made," "introduced," or "artificial." When we talk about self-sowed plants or crops, their antonyms can be those that require cultivation, which means they need to be sown, pruned, and nurtured by humans to grow and produce yield. Similarly, when we talk about self-sowed ideas, they can be opposed to those that are systemically introduced or propagated, i.e., man-made ideas that are created and spread intentionally. In short, self-sowed can be contrasted with anything that is not natural or self-originated.