Last Summer a keen poster on this forum shared a tip about propagating penstemons.
Someone had complained about a patchy strike rate for penstemon cuttings and Alan suggested placing them in water rather than in gritty compost.
I was keen to give it a try and stuck 12 P. Raven cuttings in a jam of tap water. It went on the kitchen window sill next to the over wintering cayenne chilli plant. Apart from topping up the water once or twice, Ive not bothered with it at all.
This weekend I needed the sill space for my newly sown Tomato 'San Marzano' and Itaian parsley , so I took the penstemon jar into the garden. I checked them and its a 100% strike rate! And with decent root systems too. I spent a gleeful 19 minutes potted them all up.