Rose of Sharon, known botanically as Hibiscus syriacus, is not a rose at all but actually a relative of the hibiscus shrub in the mallow family. It blooms in varied hues of pink, red and lavender in the summer and fall and thrives in full sun and evenly moist soil. Rose of Sharon is a low maintenance plant that appreciates nutrient rich soil and feeding with high-nitrogen element fertilizers.
Top dress the soil around your rose of Sharon with several pounds of high quality compost every year or two. This will feed the soil and boost its nutrient value over time. Scratch the topdressing into the first inch or two of soil but no deeper to prevent damage to the shallow roots. Percolation during watering will carry the nutrients down into the soil.
Fertilize your rose of Sharon once a year in the early spring before any new growth appears. Use a high-nitrogen granular lawn fertilizer with a 19-5-9 or similar formulation. Apply according to label directions, not exceeding two cups of product. Apply the granules around the drip line of the plant and at least four to five inches out from the main trunk of the plant.
Water the compost and lawn fertilizer deeply after each application. Lay down a few inches of organic mulch material, such as shredded bark or cocoa bean hulls, to hold moisture to the soil and prevent competitive weeds from cropping up. Lay mulch several inches out from the main trunk of the plant to prevent water wicking and rot and allow good air flow around the trunk.