When most plants in the garden are looking a little worse for wear and thinking about dying back ready for the winter, any Penstemon in your garden will still be lush and green; as well as still flowering most likely!
So now we come to the crux of the problem; to cut back, or not to cut back, that is the question I am sure would have been on Shakespeare’s mind had they been around in the 1400s! I once was informed by a customer that her Penstemon were brightening the chore off washing up after Christmas dinner as she looked out over her garden a few years ago. So do you want to remove the foliage and possibly those lovely flowers?
We here at Hayloft would recommend leaving the foliage on but still dead heading as and when it is needed. This gives the plant protection from any harsh frosts you may have and means the cold will not be drawn into the roots. You can also give them a good mulch with a heavy compost from your compost bin or I tend to use our peat based Bulrush compost, which will give them a boost of fertiliser too!