I can talk to my experience. I have 15 or so plastic pots of milkweed (like you would by at the nursury) that I have been cutting back for over a year. I never change the pot. I keep these pots because I often bring a pot indoors, cover it with a mesh net, and let the cats eat on it. At this point the milkweed in the pot is usually about 2+ feet tall. When the cats have stripped all the leaves off the plant, I take the pot back outdoors, cut it back to about 6 inches, and bring in another pot. The cuttings I put in large plastic cups that are filled with water.... cups like you'd get at the grocery store, or Costco. If the cuttings are long, as they often are, I cut them into approximately 6-8 inch lengths. While that are in the water rooting, I keep them indoors on the southern exposure side of the house. I find that if I keep them indoors I have fewer problems with the water going foul. Once a nice root ball has formed on the cuttings, I transplant them into similar cups containing a potting mix. Keep them in a shady place outdoors, and moist. You have to be careful because the roots at this point are very delicate and will easily break off. After a few weeks in the potting soil, I have nice healthy milkweed plants which I give away or plant in the garden. During the summer months this method for me has proven to be very effective. Yes, there are many other ways of doing this. During the summer months I have had good success just sticking a cutting 4 - 6 inches directly in the ground with a rooting compound.... however, the soil needs to stay moist, and preferably not in the direct sun. Some folk claim they have good luck by bending a salk over until it touches the ground, cover it with soil, and wait a couple of weeks or so and it will form roots at the point of contact with the ground. They then cut the rooted stalk free and plant. Milkweed is a weed, and it is very easy to grow. I've had as many as 100 new plants growing in the cups.