Should I trim them back for storage? They're quite large.
Winter Storage for Hibiscus
Certified GKH Gardening Expert
It is ok to trim your hibiscus plant if you are overwintering it indoors. In fact, this can lessen the stress it will likely experience while acclimating to its new indoor environment. You can trim whenever you deem necessary, but for hard pruning I would wait until spring when you set it back out. Here is an article that you may find helpful: https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/tips-for-pruning-hibiscus-plants-when-to-prune-hibiscus.htm