Last year I planted some tropical milkweed in the same bed as a swamp milkweed. Now I have all kinds of seedlings coming up.

Does tropical milkweed (Asclepias curassavica) self seed in my zone (6a), or are these all swamp milkweed? I'm only asking because I offered some seedlings of the swamp milkweed to a friend and it suddenly occurred to me that I might have more than one kind and she should know that before taking any.