Unlike in past, this year the plant has barely grown any new leaves at all - except tiny ones at the tips of the branches - despite regular watering and fertilizing with a balanced fertilizer. Cannot understand what exactly has gone wrong. Any tips or advice would be greatly appreciated.
Well Established Hibiscus Tree in Ground
Certified GKH Gardening Expert
If buds have not formed yet, you can prune the shrub.
It may be time for a good prune, which could result is loss of flowers for a season.
An overgrown Rose Of Sharon can be pruned in stages to reduce the shock, 1/3 of the shrub at a time is a good rule of thumb.
Do not over fertilize.
The articles below have care and pruning information.