Verbena bonariensis likes warm weather – they bloom in August and September. It is a tender perennial that is not hardy in Michigan. However, because it blooms the first year and re-seeds easily it can be grown as a self-seeding annual. Once you acquire it, you will always have it unless you cut every single stem.
I have had mixed results starting this flower from seed indoors. Germination is irregular and slow and some years I have planted lots of seed and only gotten a few plants. This doesn’t matter much for home gardeners who only want a few plants anyway. In future years there will be plenty of self sown seedlings to move here and there.