Hibiscus plants (Hibiscus spp.), whether hardy cold-weather varieties or heat-seeking tropical species in U.S. Department of Agriculture cold hardiness zones 5 to 11, can quickly become overgrown without regular maintenance. Not only do neglected hibiscus outgrow their pots, they also accumulate less-than-attractive growth like leggy, weak branches, dead interiors and few flowers. Reinvigorate a struggling hibiscus with a pruning plan, which can improve air and sunlight access throughout the plant, encourage branching and flowering, and reduce pest problems.
1 Select a pruning strategy. Plan to prune weak, failing plants fully to ground level for a totally fresh start and a larger number of flowers, or take a more conservative approach by thinning out only the long, leggy branches.
2 Dip a clean rag in 70 percent alcohol and wipe down the blades of the pruning shears to sterilize them.
3 Take off all dead and diseased wood in the late winter or early spring. Cut close to the branch collar at a 45-degree angle and sterilize the shears between cuts. Prune plants to ground level at this time if desired.
4 Prune long, weak-looking stems and crossing or crowded stems between February and August. Remove one-half to one-third the branch length, 1/4 inch above an outward-growing node. Make cuts at a 45-degree angle.
5 Dispose of the trimmed wood in a compost heap or trash bin. Do not compost diseased wood.
6 Water the hibiscus immediately, and continue its regular watering schedule throughout the season.
7 Fertilize the hibiscus once each week until new growth appears. Select a water-soluble fertilizer that is low in phosphorus and high in potassium, such as 17-5-24. Use a half-strength ratio of 1/2 tablespoon per gallon of water.