They look like wild phlox. Wildflower.

isn't it loosestrife,a plant that clogs waterways etc?

Not loosestrife.......definitely dames rocket....

All "weeds" are flowers we do not want growing where we do not want them growing. That means a rose can be a "weed", sometimes, as one that grows in my Lilac is.
Do you want that plant to grow where it is? Then it may well be a wild flower. If not, then it is a "weed".

Hesperis matronalis is introduced in the US so doesn't really count as a wild flower, not being a native species. It isn't native in the UK either but I like it when it shows up in my garden and do not consider it a weed. In other people's gardens it may be.

I had one of those come up in my shrub boarder last year. Dame's Rocket for sure. It smells wonderful in the evening, like the sweetest Stock!

I guess it might be a pest some places, but even though I let it go to seed, it never came back. We are pretty hot and dry here, so maybe it needs more moisture. I'd take it over Cats Ear and Bindweed any day.

This post was edited by BarbJP on Tue, Jun 10, 14 at 0:17

Yep, one i have sowed in my shady woods . comes in white too - will seed around so remove seed heads (long strips like very thin pods) if you don't wish to be overwhelmed.