Milkweed does contain toxins that can be harmful to pets, livestock and people. The milky sap for which it gets its name leaks out from the stem or leaves. This sap contains toxins called cardiac glycosides or cardenolides, which are toxic to animals if consumed in large quantities.

Why is planting milkweed illegal?

Milkweed can interrupt monarch flight patterns

Monarchs are not supposed to breed on the coast, so there is no need to plant milkweed here to help them. ... So the rule is: If you live along the California coast, plant nectar plants to support the monarchs migrating to and from overwintering sites; do not plant milkweed.

Is milkweed toxic to humans?

Milkweed contains cardiac glycosides that are poisonous to humans, but the level of toxicity depends on the species, age, and how it's prepared and eaten. ... Milkweed poses the greatest danger to grazing animals, but there are reports that show that animals avoid it.