How to Prune penstemon 'Purple Bedder'?
For herbaceous perennials that die back, cut dead stems near the crown without damaging new shoots; retained winter stems can be removed in spring. For tender woody perennials such as penstemons, wait until frost risk has passed and shorten old stems just above healthy new growth. Evergreen perennials are tidied by removing dead foliage rather than cutting the whole plant down.