Welcome to the forum! I think I know. The seeds pods look exactly like those of "Hesperes" or "Dame Rocket", both the same plant. I love them. Biennials. They self-seed however, so there always are plants. They look very similar to Phlox but have the strong aroma of Lilac. Love them. They range in colour from white, mauve, pink, purple, etc. Great bouquet if cut young before the flowers have opened. You can vollect those seeds, and start them inside now. Otherwise, sprinkle the seeds wherever you would like to have them grow. Beautiful plant! Cheers!