Penstemon cuttings
If penstemons have a failing, it is that they are not long-lived. They may not survive very wet or frosty winters. And like many other evergreen perennials, they can grow woody after a few years' growth. But don't be put off. They are dead simple to propagate.
Cuttings can be taken almost all year round, if you can give them some bottom heat, but propagating in late summer (July to September) will give you nice bushy plants for next year.
Select non-flowering, soft stems and take cuttings about 10 centimetres in length. Carefully remove the lower leaves and insert the cuttings into a pot of moist, gritty compost (one part multipurpose compost and one part coarse sand). Firm the compost around the cuttings.
Cover the pot with a tent made from a polythene bag and put in a bright place indoors (or in a greenhouse or cold frame), out of direct sunlight. The cuttings will root in a few weeks when they can be potted on and overwintered in a greenhouse, cold frame or very sheltered spot outdoors.