Yup, it's purple loosestrife. As far as I know, it's been "cultivated" for a very long time in Europe/Eurasia and some parts of Australia and Africa, as there are several native varieties in those parts of the world. However, it's on the noxious invasive species list in Canada (and probably many US States which still have "wetlands"). In the 80's greenhouses here sold a supposedly "sterile" variety, which turned out to be false (sort of like Jurassic Park, nature will find a way lol). Over time the plants reverted. It's a serious problem here, but not in Europe. Greenhouses here in Edmonton have been more or less prohibited from selling the plant since the early 90's. In North America, there are much better plants to attract beneficial insects as well as my favourite - hummingbirds. Apparently it is now a problem species in New Zealand as well.
Here's a link, if anyone cares. Things are much worse in Saskatchewan, Manitoba and Ontario than they are here in Alberta, but I thought the Alberta government info had a nicer layout as a webpage lol: ABgovtagri
Howie: that's really cool about the observatory. I must confess that I didn't know there was such a thing as a "Dark Sky" phenom. It's amazing what you can learn from a photo thread. Thanks for posting it.