Hi

I planted a Melanthus major in the early part of the year when it was about
2 feet high. Its gone absolutely crackers this year and now stands approx 7
feet high with 4 very large flowers.
I have 2 questions really:

1. Does this plant need pruning/cutting back? If so, when should I do it
and how far do I cut it back?

2.After a particularly hard frost last night, It is looking decidedly sorry
for itself, all the leaves are limp as are some of the flowers, Will the
frost have damaged it, or is it just sulking?

Thanks for any advice

Rick