Perennial hibiscus (rose mallow) can be pruned in the spring, just as new growth begins to appear. To keep it under control (once you’ve pruned it back), just pinch the tips of the stems regularly. This will encourage new growth near the center of the plant.
If you’re growing Hibiscus syriacus, or Rose of Sharon, you can cut back the previous season’s growth. Cut it back in winter, leaving just two buds, and in the spring new growth will appear.