Silene armeria or Sweet William Catchfly is in the database. I've never heard the reference to Sweet William before. When it flowers, if you grasp the stem just below the flower base, you'll find a sticky bit. Thus the name Catchfly. My father got a free packet of flower seeds in the early 1950's. From then on we knew it as "Dad's Surprise Package Flower." It followed us in all of our moves, not that we ever intentionally took a plant with us. I finally identified it a few years ago. I find it to be biennial - it will seed and start it's plants in the fall, and continue coming up all spring.
They settle themselves in wherever they can. But they are easily removed, if not wanted.
