In particular.... I have cut back a specimen I acquired very heavily and am hoping it will shoot back from old wood? I was on the understanding that they do, but in hindsight I should have asked here before doing it

Can you cut back the roots hard, and I presume Spring might be the optimal time? Being a swamp variety I am guessing lots of water for a while after the repot.
Any help from those that grow this species would be greatly appreciated please.
