Zinnias are supposed to be annuals but ours have reseeded themselves every year. Every year I wonder if these flowers will come back. My husband always assures me that they will and he's always right. Actually, they are spreading and now cover parts of two flower gardens. Along with the coneflowers I started last year, our garden has become a butterfly and moth haven.
So now we not only enjoy a variety of zinnias, we get to see an increasing variety of winged creatures enjoying our flowers, too.