Milkweed is a group of plants named for their milky sap. They’re an important nectar source for bees and other insects, and serve as host plants for certain butterflies. In fact, milkweed is the only plant material monarch caterpillars can eat.
Also known as butterfly weed, milkweed is a perennial native with orange or yellow flowers that appear in late summer and early fall. It attracts queen and monarch butterflies for nectar and larval food.
Source: UF|IFAS Gardening Solutions