Some people use the terms “milkweed” and “butterflyweed” or “butterfly weed” interchangeably, but they are not exactly the same thing. “Butterflyweed” or “butterfly weed” refers to the species Asclepias tuberosa L. As you can see, this is a member of the milkweed genus. So, a butterflyweed is a type of milkweed, but not all milkweeds are butterflyweeds. Try to only use the term “butterflyweed” when you are referring specifically to this specie. Otherwise, say “milkweed.”