Florabunda sells those seeds as do Urban Harvest. I grow these plants easily. they even sprout between my interlocking. What are you doing that you have trouble growing these plants/ They should be fine in your zone. If you cast those seeds out now, it will still grow to full flower by summer. My plants germinate from seeds casts about by the previous year's plants. I also amend it further with new seeds. All I do is to sprinkle (not cover) the seeds as it needs sunlight to germinate. .

Also, even though the stems are long and thin, they are very strong and not floppy. They're kind of similar in appearance to tall garden phlox, but the flower heads are smaller. They also reseed themselves very nicely-they're not garden thuggy at all. Mine's in a tiny bed by itself this year, but I like your idea of mixing it with the milkweed. Although you don't want to mix a thickly growing plant with your milkweed, one that I have found that really attracts zillions of butterflies is blue mist flower. It spreads from the roots and will take over an area. But it's easy to pull out because the roots are very shallow. It blooms from early Spring to late fall and has fuzzy looking sky blue flower heads and bright light-green foliage. For being on the verge of thugism, it's really a pretty butterfly attractor. Cheryl

I got it at Portland Nursery on Stark in (obviously) Portland... when I called they said they had one blue and one white, and while I was poking around I found two more blues in their display area. I bought all three blues and may have depleted their supply of that color. They do have a second store and it's possible they have it there. According to their web site, Joy Creek has it (www.joycreek.com), near Scappoose... they do mail order if you can't find a source closer to you. It's a charmer and I'm really glad I found it. Good luck!

Ha, I intentionally PULL the ones out of the more wild area here because I don't want them to get away and become invasive. In central PA (I'm also in 6A) V. bonariensis self-seeds very readily. The butterflies love it though so I continue to let it grow here, pulling all the extras out every year. If I don't, I think it would totally take over and crowd out all of my other garden plants except maybe the coneflowers. I don't have any other garden plants here that seed so vigorously, and I have a lot of different kinds of plants since I've been butterfly gardening since 2005. V. bonariensis is the very first plant that I saw my first Giant Swallowtail nectaring on. It's a great plant to have for them in the garden, but I control its spread and limit it to my garden and ONLY in the section that has been allocated for it.