Doellingeria
Previously known as Aster umbellatus, but is now one of three species in Doellingeria, with only the flat-topped aster in UK cultivation. Native to North America. Generally, small, but many flowered.
Irrespective of the intricacies of taxonomy, all former species of Aster are of immense value to pollinating insects, especially butterflies, bumblebees, honeybees and hoverflies, particularly in the late summer to autumn garden.