Common Milkweed (Asclepias syriaca)

Q: If I wanted to seed about nine acres of property to "give back" to nature, how many pounds of seed would I realistically need to adequately cover? I would expect that I could purchase less than a full 17 lbs per acre, with the idea that this plant will spread, and allowing some other wildflowers/plants to grow between the milkweed would be okay as this seems natural.