Q.When to prune?
My hibiscus looks dead. Do I need to prune them?
Certified GKH Gardening Expert
This article will help you determine if they are dead or not:
https://www.gardeningknowhow.com/plant-problems/environmental/how-to-tell-if-a-plant-is-dead-and-how-to-recover-an-almost-dead-plant.htm
They do not need to be pruned, but if you want to prune them to shape them or reduce their size some, then you can remove up to 1/3 of the plant. This article will help as well:
https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/tips-for-pruning-hibiscus-plants-when-to-prune-hibiscus.htm