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
'Sour Grapes' is an erect perennial to 60cm in height, with lance-shaped leaves and dense panicles of tubular, two-lipped flowers blending purple and blue shades, whitish within the throat