I too love Verbena bonariensis, I grew it from seed many years ago. I took plants with me when my husband and I moved to Spain and they self seeded prolifically around our plot in the mountains and looked great growing alongside the wild flowers and grasses. My Spanish neighbours loved them too. We returned to the UK a few years ago and brought our plants back with us. Unfortunately the severe weather we had last winter killed off my large Verbena bon. plants along with several others, but luckily I never cut down my perennials until Spring and now have lots of seedlings popping up everywhere, I just dig them up and move them where they are needed or pot them up and give them to family and friends. I have two wonderful Lupin plants that suddenly appeared last year as seedlings also oriental poppies spring up everywhere, I've never planted any neither have my neighbours so I presume I have the birds to thank. When my foxgloves and aquilegia seed pods turn brown I assist them by giving them a little shake, then cut some off and scatter them elsewhere - I just love plants for free.