Here’s a plant that you should consider for long season interest. Sturdy 2′ stems are clothed with delicate fine needled foliage, reminiscent of Amsonia hubrictii, gradually forming stands 2-3′ across. Vernonia lettermanii remains attractive all summer, and in early September, clusters of purple aster blossoms top the stems, inviting myriads of monarch butterflies. Picture this little gem planted with Sedum ‘Maestro’, Anemone ‘Honorine Jobert’ and Calamintha nepetoides and you will no doubt pleased by this end of the summer vignette.
Just about all of us can grow Vernonia lettermannii . Native to the Ozarks and found in rocky flood plains, this compact species of Ironweed is very tolerant of hot dry locations, yet can withstand brief periods of flooding. This means it is quite adaptable to soil types. It can be grown in gardens ranging from zones 4-9, adding one more plant to cold climate palettes.
Undemanding and lovely, Narrow Leaf Bluestar begins to charm in late spring, bearing clusters of light blue star shaped flowers at the tips of it sturdy 3′ stems. The foliage which cloaks the stems of this species is delicately narrow, adding a soft texture to the mixed border all summer long. However, it is in October that we think it becomes most dramatic. 
Little has been written about this lovely late summer/fall blooming Asian Aster. It came into our possession last November, via US Mail, swaddled in newspaper and still covered with blossoms. The return address cited Margie Mott as the sender, an old friend and plant huntress who scours every nursery and garden center on the eastern seaboard. She had lost the plant’s name tag but thought she had acquired it from Asiatica Nursery, which, you may have heard, sadly closed their doors this season.