I consider the A. curassavica to be native here, and not a problem. There's no Monarchs here during the winter in any case. All my milkweeds that were in the ground went completely dormant this winter and only recently I saw growth starting on them. I just hope that if any Monarchs do show up and lay eggs, there will be enough foliage. The milkweed I have in pots aren't very big yet either. I'm hoping for lots of little seedlings this year!
