Your herbaceous perennials tend to look a little worn out by mid Autumn, and it’s a good time to prune them back to the ground. Alternatively you can leave the pruning until early spring to retain winter interest, and importantly a food source and habitat for wildlife.
The more tender perennials like penstemon, should be left so that their woody stems offer some protection in the colder months. These can then be cut back in early spring once the frosts have passed.
Other more evergreen perennials such as kniphofia, agapanthus and tulbaghia should be left and tidied in early spring.
Pruning of ornamental grasses is best left until spring, cut back old foliage as you see new leaves emerging.
If you do cut back your herbaceous perennials this autumn applying a good mulch afterwards is a great way to make sure they are nice and snug for winter.
If pruning is left until spring take care to avoid damaging new shoots.