I'm after opinions on pruning Verbena bonariensis. Mine is *still* flowering and in the past I'd read cut it back in March but I've since read some say cut it autumn 'after flowering'. Also when you cut it how low so you go ? I've cut it low and lost plants in the past but when I've cut it higher it's only sprouted from near the cuts and not the base which gives a straggly plant.
What do you do ?