Garden Flowers And Garden Ideas : Coreopsis 'Star Cluster' blooms June – September but cut back after firs… July 10, 2018 0 2966 Flowers And Garden Ideas : Coreopsis 'Star Cluster' blooms June – September but cut back after first flowers fade to promote further flowering. plant in full sun in any good garden soil…'Star Cluster' grows about 18″ tall and wide…hardy zones 5-9