Here is the link to the MW photo of sand sine...
I too, would love to try to grow this plant. If it is native to southern regions, does anyone know how far north it will grow? I do know it is popular (with monarch folk) in Ohio, so hope it will be hardy in central Ontario too.
All milkweeds are usually listed as invaisive, but they are harder to grow from seed than you would expect. Like most perennials, they take years to get established and mature. I have sown many species and it is a slow process to create a plot that you can actually use as a source of cutting to feed caterpillars.
This year, I had a good crop of various milkweeds germinate, but my biggest problem was that insects were eating the seedlings to the ground. I am hoping the roots may resprout next year.
My most successful species from seed has been A. incarnata (Swamp Milkweed) followed by A. tuberosa (Butterfly Weed).
Although rare around here, I found swallowwort growing along a rail trail (former rail line, now a bike/walking path). Being curious, I pulled a small plant as well as gathered seed. The plant has existed for a couple years, not really getting much larger, and the seed never came up. So much for the invaisive habit! I figured that we would watch for any eggs that might get laid on this plant and bring them in to put them on proper milkweed. The monarchs never gave this swallowwort a second look.