It depends - if you don't cut them back, what'll happen over time is you'll get long, thin and straggly, leafless stems trailing down for the first 2-6 inches with green growth dangling at the bottom. If the wall is above head height, that might not matter too much, but if its a lower wall, you'll see the top of the plant as well. I'd cut them back...

Agree with Bamboo… they get seriously straggly unless cut back and simply look a mess.

Many thanks, I see them beautiful masses trailing down some walls, I will train them carefully trimming them.Thanks.

trim as if you were putting layers into hair. That way the shorter leafy stems hide the longer straggly stems.

Good Idea E'n good to see you are still around supporting us!!

I rarely go away Thelma ;o)

sorry not convinced. We cut back hard every year and it grows and trails down the side of the raised bed.

I never cut mine back. My wall is about three and a half feet high. It is rocks, cemented in. Somehow over the years soil has got in cracks and new plants start. Our wall is a mass of colour in season. It doesn't get a lot of water either and no fertilizer although our soil is good. I will try and enclose a photo.
I have got two photos on here but I don't know how to get them here.
Clementine

You can't add photos to answers you'll need to post in your own pix.