This common plant is easy to identify.  Milkweed has large opposite leaves, large 2-4" clusters of small pinkish green flowers, large warty seed pods, and exudes a sticky white sap when broken.  This sap is poisonous to many birds and mammals and there are some insects that use this to their advantage.  Red Milkweed Beetle and Monarch Butterflies (larvae) are two species always found close to milkweeds.  These species eat the sap and store the toxins in their bodies.  They are often brightly colored to advertise their toxicity.
    Common Milkweed is found in fields, roadsides and waste places where the distinctive foliage, flowers, and seed pods alert their presence.