Looks like a very compact form of Wand Flower, Oenothera lindheimeri 'Siskiyou Pink' (formerly Gaura lindheimeri),

Yes. And it's perennial.

It will be iffy whether it will come back in your zone. I grew O. Whirling Butterflies and it came back smaller & weaker the next two years, then gone. A very common issue here.

OK. Botanically perennial, to be more precise.

Thanks, all! I quite like it. Had three big flushes of pretty blossoms, so basically constant blossoms.