Some tender perennials are grown as annuals, such as the sunset flower, which blooms from late summer to early autumn, and the blue spirea that blooms in early fall.
Many fall-blooming annuals start blooming in the spring or summer and continue blooming into the fall. For example, the blue daze blooms from spring to fall. However, the flowering cabbage blooms from fall until spring. Brightly colored zinnias also bloom in the fall months.
Since "half-hardy" plants require longer periods of growth, plant them indoors, about four to eight weeks before the last frost of the season. Transplant the flowers outside around May when all danger of frost has passed.