Question

My cordylines have been damaged by heavy snow and now the tops are bent over. What do I need to do to help them recover? 

Answer

The damage is now done, I would just leave the plants and see what happens as the weather warms up.  If only the stems have been damaged the plant should shoot again from any undamaged part or at the base of the plant.  If and when the plant re-shoots, cut off any damaged or dead wood above the shoots. 

If the ground has been frozen and the roots and base have been damaged, I'm sorry to say the plant has probably gone to God.