Does swamp milkweed spread at all? How quickly? I'd really like it spread some. I'd like to have at least a small patch, not just a plant, LOL.
Missa, do you intend to grow them from seed, or purchase plants?
Asclepias incarnata is perennial and seeds need to be stratified for at least 30 days to break dormancy. It's probably early enough you could do that in the fridge with the baggy/sand method, and then pot them up into small pots to grow them on for a bit, and then transfer to the garden.
My A. incarnata didn't really spread that much since it is a clump-forming milkweed rather than one that spreads by runners or rhizomes. A plant can eventually get about 3-4' tall and as wide.
If you want a plant that spreads by underground, you might want to choose either Asclepias speciosa or Asclepias syriaca to start with. Both can be invasive, but it sounds like you might have an area to dedicate to a milkweed that spreads. Seed preparation is the same for these milkweeds. I have A. speciosa and grew it from seed. This is its 3rd year. I only planted 3 or 4 plants, and it has already increased exponentially, and is flowering this year as well. Lots of butterflies, moths, and other insects are attracted to the fragrant blooms, which are gorgeous.
If you don't want to worry about a plant that spreads like these two, I recommend you plant several A. incarnata in your patch.
In late spring, I always plant seeds of Asclepias curassavica aka Tropical Milkweed, or Asclepias physocarpa, Oscar Milkweed, which are annuals in Oklahoma. The Monarchs, however, actually prefer to lay eggs on these two milkweeds. You just can't have too many milkweeds for the Monarchs, lol! The seeds of these do not need any cold treatment, and usually you will get seed pods at summer's end to save for the following year.
Purple Milkweed is excellent choice for a plant that will spread out some, but not take over. It has gorgeous flowers. Marilyn Stewart of Wild Things Nursery in Seminole is growing and selling it. You can go to her web page and see a schedule of where she will be selling. Contact her about the Purple Milkweed. Tell her Sandy sent you!
She also has the other milkweeds for sale as well. I just got some speciosa from her last weekend.
Asclepias incarnata is a clumping milkweed. It does not have tuberous roots and doesn't spread by runners. It's very easy to start from seed however, and you could plant several seedlings together in a patch.
From seed, it usually doesn't bloom until the 2nd year. But I grow seedlings almost every year, whether they thrive or not, because the female Monarchs love to lay eggs on the small plants of swamp milkweed.
I actually found a small plant at a plant farm yesterday. It has 3 stems growing.