Penstemon ‘riding Hood Delft Blue’ Really Is One Of The Best Flowering Perennials You Could Include In Your Garden. They Start Flowering In Summer & Continue Through To Autumn. Deadheading Regularly Will Help Promote These Flowers. They Are Drought Tolerant But Will Thrive In Moist Soils, They’re Unaffected By Heavy Rain & Resistant To Slugs & Many Other Pests. Perfect For A Mix Herbaceous Border As Well As Containers In Sun Or Partial Shade.