Milkweed for Monarchs Milkweed is the host plant for Monarch butterflies. The female butterflies lay their eggs on milkweed so the caterpillars can eat the leaves which allows them to build up a toxin that makes the caterpillars and butterflies undesirable to predators that may try to eat them. This toxin is also dangerous to … Continue reading Milkweed for Monarch Butterflies