Phlox paniculata.

It's wonderful! Enjoy it! Perennial. Comes back every year. I love it in my garden!

thanks for the responses! any idea how to cure the mildew developing on the leaves?

If the mildew problem isn't bad (and it doesn't appear so from the photo), you can pick the affected leaves off and make sure to water from the bottom in the morning, so that any water splashed onto the leaves can evaporate quickly. If it's a more serious issue, a copper spray is usually the best place to start, though some folks swear by neem oil.

Try diluted milk. I didn't believe it, when someone here rec it, but I tried it on my peonies, never had it again. Tried it on Queen Elizabeth rose, same result. Think they used skim milk.

thanks for the responses!