This is a beautiful, self-sowing annual that grows well on the roof. The plants that self-sow grow taller and bloom for longer periods than the seeds that I tenderly plant and then transplant. The hardiest plants came up between the cracks of the roof tiles. It makes a great fill-in the spaces between taller shrubs and border annuals.
I fell in love with this plant at the Brooklyn Botanical garden and was happy to find seeds online. It blooms from August through September and takes the heat pretty well.