Flowers That Plant Themselves
Sure, they're called annuals, but buy their seeds once, and you'll have blooms year after year.
Each one derives much of its seasonal color from flower seeds you buy and sow only once -- plants such as poppies, larkspurs, coreopsis, and cosmos. After they finish flowering, their seeds drop to the ground, and then new plants magically appear the following year.
Self-sown seedlings, often called "volunteers," sometimes show up in unexpected places -- gravel paths, cracks between rocks, or right in the middle of a clump of something else. This randomness gives a cottage garden its charm and surprise. And if you don't like where something sprouts, it's okay to yank it up.