Hesperis matronalis

Dame's Rocket (Hesperis matronalis) is not a true North American native. Dame's rocket, also known as dame's violet and mother-of-the-evening, was introduced as an ornamental around the time of European settlement. It continues to be widely used as an ornamental and can be found throughout North America. Hesperis matronalis is not phlox & not related to phlox. There is an easy way to tell the difference; sweet rocket flowers have four petals and phlox has five. Also, sweet rocket leaves are alternate and phlox has opposite. The plant is part of the mustard family, which also includes radishes, broccoli, cabbage, and cauliflower.