To keep the beautiful blooms of your rose of Sharon shrubs coming, sometimes a good dose of fertilizer is all you need. If you aren't sure how to feed a rose of Sharon shrub, don't worry, it can be fairly easy and takes less than 20 minutes to do. When feeding your shrub is paired with pruning, you'll find you have a well growing, rose of Sharon with attractive and colorful blooms on stems which can live for decades.
Check the height of your rose of Sharon in spring by measuring it from the ground to the upper most branch. If your plant has been pruned it may be easy to measure, but taller plants can be a little more difficult.
Measure out one tablespoon of fertilizer per foot in height of your plant. Be sure to use a tablespoon which is solely for garden purposes and not used in the kitchen.
Sprinkle the correct quantity of fertilizer in a ring around the base of your rose of Sharon, being careful not to let the fertilizer touch the shoots and trunks of the plant directly.
Cover of the fertilizer with two to four inches of mulch. This will keep the fertilizer from running off as well as prevent weeds and help maintain moisture in the soil.
Fertilize again in midsummer by raking back the mulch and sprinkling the granules. Because the plant has grown, you may need to measure the height of your plant again to see how much fertilizer to use. Replace the mulch when you are done.