I keep Asclepias curassavica in pots year round, since it is not winter hardy in this area, I bring the pots into the garage during freezing weather and out again when it warms up. This way I have fresh and growing milkweed for the monarchs when they come by in the spring.
Also having the plants potted allows me to move them around to good locations and I can keep them watered more easily.
It works very well for me and the monarchs.