Penstemon pruning - how far down should I go?

I got these penstemon plum jerkum perennial plants last summer (purple flowers), and they survived winter. I didn't prune them last year.

For spring pruning, do I follow each old stem up from the bottom and then prune above the first new green shoot - even if that shoot is tiny? I can see some where it's about a 2mm tiny green shoot.

And if i don't find any new green shoot on the old stem, how far up from the ground level do I prune the stem?

(I would leave alone the few totally new tender stems coming up which are about 3-4 inches high.)

I'm finding it a bit confusing as the old stems still look so green.

Many thanks.

 

I would just leave those to get on with it. They're still young plants. Even the "old" stems don't look particularly old/woody/knarly and I think they'll flower well. Maybe prune off the older stems after they've flowered, particularly if they get too heavy and flop all over.

 

Thank you I will do that, I really didn't know what was best! They do look so green, which is why I was hesitating to folllow the standard 'spring prune' advice when I do an internet search on them.

I got them as young plants from the supermarket in mid-late summer last year when they were just starting to flower, so they are still young.

I did cut off a couple of obvously dead looking stems a week ago.

For the rest of the stems, maybe I can tie them to bamboo stakes if they flop while still in the flowering stage.

Do I prune off the older stems at ground level if they've finished flowering at the end of the season (and especially if they have flopped over), or where is it best to cut them? and is it best to leave rest of the stems as they are after they've finished flowering, and then wait until next spring to reassess?

 

IMO it is best to leave the stems as they are at the end of the season to give some degree of frost protection - not all penstemons are hardy. You could shorten the very tallest stems by half if it looks untidy and bothers you.
When you see new stems growing in the spring, it indicates that the soil is warming up and the likelihood of frost is diminishing - depending on where you live of course. Then you can cut down the old stems.

 

Some winters my penstemons don't seem to stop growing so it's a judgement call when and where to cut back. I often take a few long ungainly branches out in late summer/autumn leaving the rest to overwinter, and it doesn't seem to do any harm. Admittedly mine are hardier types, "Garnet" and "Stapleford Gem".

 

Thank you both for your replies, very much appreciated!