I ordered A. tuberosa and A. verticillata (Whorled Milkweed) last fall from Monarch Watch. About half the native milkweeds in my area require moist or swamp-like conditions so that automatically ruled them out. The plugs transplanted really well and a few of the Whorled Milkweeds even bloomed! The only milkweed plants you can buy easily around here is the Tropical Milkweed and I'm trying really hard to go native. You can find A. tuberosa seeds pretty easily, too. I didn't plant all the plugs in case some died (one did) and I didn't have enough room at the time so I still have some planting to do. I'm curious to see which species the caterpillars prefer and how they fare on the plants.
