Hi Mary Ann,
I have not saved seeds from it recently, but if you post on the seed exchange forum here:
https://garden.org/forums/view... you may find some.
I have grown them a few times, always in containers because of my heavy yellow clay, and the hummingbirds did love them. I enjoyed the salmon-red color. Mine got taller and lankier than hybrid Petunias in general, but I don't recall the root system taking any more space than other species. I think those in the photo are growing in an old metal bucket and they were accompanied by something else in the same container, but I can't remember what. Anyway, that bucket was on the small side, probably about 3 gallons. I have also grown them in a window box so that I could watch the hummers from inside, but after one of the birds flew forcefully into the window I discontinued that practice.
If no one in the garden.org exchange has them, you might try the GardenWeb Seed Exchange on Houzz.
http://forums2.gardenweb.com/f...
I hope you find them. They are worth the effort.
