Is the bloom time of Asters really that short? According to this website Smooth Aster blooms from August - October.
http://www.wildflowerfarm.com/...
Smooth Aster is one of the most attractive and long-lived of all the asters. Blooming from late August through to the end of October, it puts on a fabulous floral display producing clusters of dainty blue flowers long after most flowers are finished. A favourite stopping spot for butterflies, this Symphyotrichum laeve (formerly called Aster laeve) does well in just about any well-drained soil.
