the.com/milkweed

means A wild perennial plant with milky sap that produces pods full of silky-tufted seeds, and that serves as the exclusive food source for monarch butterfly caterpillars.

from The name is a plain, literal compound: 'milk' plus 'weed,' describing the thick white latex sap that oozes out when you break a stem or leaf. That sap is mildly toxic, packed with cardiac glycosides the plant uses for defense — and which monarch caterpillars co-opted, eating the leaves and sequestering the poison in their own bodies to become distasteful to predators. 'Weed' here just marks it as a wild, unbidden plant rather than a cultivated one, the way English has long lumped uninvited greenery together regardless of its actual worth.