Part of the Pristine Series, this improved Penstemon’s sturdy stems are covered in tubular sapphire-blue flowers from early summer to early fall. More cold hardy than older varieties, ‘Pristine Blue’ is also drought tolerant once established and irresistable to pollinators.. Mature Size: 12″-20″ x 12″-18″. Full Sun (6+ Hours), Morning Sun Afternoon Shade.