Gardens are all about balance. A garden is out of balance if the weeds are spreading faster than they can be controlled, or if cultivated plants die, fail to thrive, or grow so aggressively as to overwhelm neighboring plants and the gardener's ability to contain them. I like an informal, naturalistic garden in which everyone "gets along." Gentle spreading and occasional self sowing are signs of satisfied plants growing well in the environment provided. Their gentle self-sowing adds to the naturalistic affect while adding bulk makes for more flowers and opportunities for division. I recall my mother complaining about Fritillaria meleagris (guinea-hen flower). She said, "You plant one and you get one." What she meant was that it never increased in size or spread about. I wish she was still around, so I could share my pleasure in seeing mine multiply. (She was always my best garden confidant.)
Clearly we want a bit of reproduction among our plants, so discovering seedlings of these three (pictured) all in one day was a genuine source of pleasure.