How to prune a Solanum crispum 'Glasnevin' Potato Plant

We have a Potato Plant in our garden which we have had for about three years.We have never pruned it and do not know how to start and where to start.It is now getting quite large and spreading.We have a passion fruit plant next to it and it is now starting to take that plants space.Any advice appreciated

 

Hi,i had the same problem,i just pruned it all the time,it grows so fast it was hard to keep on top of!...i hacked it down to the ground a few week back and hope it doesnt come back as i had clearly planted it in the wrong place.
Here is a pic,the purple mass behind a work friend

 

I had a solanum a few years back , nice flowering shrub. I pruned it back to waist height in Feb-March , this worked fine. For some reason I cut it back to 6" from the ground one year . That did not work

 

I sawn mine to 1mm above the ground @HarryS thanks for confirming itl never come back
Ive got a cutting somewhere if you want it x

 

pity it dont grow spuds

 

Spring is the best time to prune it and you can chop it back by a good third.

Now it the time to take cuttings for propagating which, to my mind, means that you could cut back some of the soft growth to tidy it up a bit. Problem with that is, of course, you would lose out on their beautiful flowers by doing it this time of year.