Best time to prune Verbena Bonariensis

Hello, I have some VB in pots which do quite nicely each year. I do need to repot for next year, and cut down, of course. When is the best time and how far, ideally, should I cut back? Thanks!

 

@ennnceee I grow this in borders around the garden, it self seeds happily. I tend to cut it down to about 6 inches above the ground between now and spring as I tidy the borders up.

 

I still have bees visiting mine and when the seeds are ripe Goldfinches sometimes feed on them so I don't cut mine down until December but anytime after the flowers have died and turning brown will do.

 

Thanks all!