Propogating Penstemon

now is a good time. choose a non flowering shoot and cut about 2-4 inches from the tip.
remove leaves leaving 3-4 intact.
i plant mine into a gritty compost with out rooting powder [but you can use it if you want].
I put about 4-8 cuttings around the edge of a 3" pot. water well and then pop in the coldframe or on the windowsill or in a propagator. hopefully in a bout a monh roots will be forming.
in spring i cut mine back and use some of the stems as cuttings and pop them in a heatde propagator.

Perfect advice from Seaburngirl...
I'll add that you could try starting a couple of cuttings in a small container of rainwater. My recent blog on cuttings in rainwater has some interesting comments from members.
I hope this helps...
... and, Leebugs... welcome to GoY :o)