I also have them in my yard under windows, I have a ton of left over seed. Mine had two spires of flowers on each stalk. Since they only bloom every two years they are a fascinating plant. Glad to see others have these. They are very hardy handle extreme heat and cold with ease. Mine are covered in snow and still standing tall!
I forgot to mention that they love sandy soil. I actually planted my first one in the old tire sandbox and it is thriving. Not trying to take over your auction, just help you promote with a few first hand details.