Dame’s Rocket (Hesperis matronalis) lights up the hillsides of Pittsburgh in late spring. Pittsburghers commonly refer to it as “phlox,” but it’s actually a member of the crucifer or mustard family, as you might guess by its four petals in a cross shape. It’s a foreign invader, a descendant of garden flowers brought by the first European settlers. But who can object to a weed as beautiful as this? The flowers commonly come in a range of colors from vivid purple through pink to white, but some patches have bicolor flowers delicately spattered with color in an infinite variety of patterns.