Superb Penstemon, Coral Penstemon (Penstemon superbus) . Will re-seed and interbreeds freely with Parry’s Penstemon (Penstemon parryi). . Penstemons are one of the most valuable late summer-flowering perennials and, in all but the coldest regions, are easy and reliable. . Penstemons a large genus of North American and East Asian flowering perennial with wands of coral, treet-shaped flowers that appeal to hummingbirds. Best planted in full to part sun locations.