August 29th - September 4th
If you have penstemon hybrids in your garden, they have already produced their first flush of flower. Cut back the spent stalks to a clean node (the leaf joint on the stem) just beneath where the lowest set of flowers has faded. More flowers will be produced from side shoots and from shoots coming up from the base of the plant.
Penstemon cuttings can be taken at almost any time but September is recommended if you want plants that will perform well next year. Choose non-flowering, soft (but not floppy) stem tips and cut immediately under a node so that you have about three or four inches of material. Insert cuttings either singly or severally into pots or trays of moist gritty, free-draining compost. Cover with a polythene or translucent plastic cover to maintain a humid atmosphere, and place in a bright, warm place indoors, out of direct sunlight. When the cuttings have rooted (a few weeks) they should be potted on without delay and over-wintered in a greenhouse or cold frame.