Penstemon may be deciduous or evergreen perennials or subshrubs, with simple, narrow leaves and racemes or panicles of bell-shaped or funnel-shaped flowers in summer and early autumn
'Raven' is a semi-evergreen perennial making a clump of stiffly erect stems to 1m in height, with narrowly ovate leaves and panicles of deep purple, bell-shaped flowers 4.5cm in length, the throat white, striped deep red