Best seen on black. Our neighbour has a Loosestrife or better known as Bluestrife (Lythrum salicaria) in her garden. I noticed that it didn't bloom this year, but also noticed, for the first time that I can remember, it changed colour in the fall and looks quite beautiful.
to read up on this flower I include this link http://www.invadingspecies.com/invaders/plants-terrestrial/purple-loosestrife/