Buy Penstemon 'Raven' from Sarah Raven: An absolute top favourite - it's a delicious, strong, deep purple with large flowers. It's a strong grower and one of the best for arranging, lasting well if the stems are seared.
Penstemon 'Margarita BOP' and 'Firebird', Beardtongue Penstemon are gorgeous specimens for the dry, arid garden. They thrive in areas with low fertility and well-drained soil. Margarita BOP is compact with showy spires of iridescent blue flowers May through September that fade to purple. At the same time the semi-evergreen Firebird explodes into bloom with tubular scarlet flowers. Some of the best things about Penstemon are a second flush of flowers in July and they attract hummingbirds.