I received this in a round robin seed swap. I planted some last year and they did nothing but spread with runners. This year, it decided to go vertical. The label on the seed envelope was "Beautiful pink flower by deck". Any ideas? Thanks in advance. Edit: I have not seen it flower yet.
Looks like Great Willowherb Epilobium hirsutum to me. Often considered a weed ;-) Pic: http://ip30.eti.uva.nl/BIS/flora.php?selected=beschrijving&menuentry=soorten&id=3046