My neighbor has this plant in rock by her mail box. It is so pretty. She doesn’t recall the name of the plant
It is a type of loosestrife. At least one variety is considered a noxious weed in many areas so call your agricultural department or local extension center to learn more before buying any.
https://www.gardeningknowhow.com/plant-problems/weeds/purple-loosestrife-info.htm