Hibiscus is a hardy, deciduous perennial that produces large, saucer-shaped pink, blue or white blooms from July to September. The plant is long-living. It benefits from being fed in spring and again in midsummer, which enhances flower production. You can choose between organic or nonorganic fertilizers.
Fish meal, is an organic fertilizer that adds nitrogen (between 5 and 8 percent) and phosphorus (5 percent) to soil. Fish meal is dried fish that has usually been turned into powder, which can be used as fertilizer. Fish meal is a fast-acting fertilizer that works well for all soil types. You can buy fish meal or other organic powder fertilizer from garden stores. Follow the directions on the package and work it into the soil
Purchase dried seaweed at a garden center and work it into the soil around hibiscus plants. If you live near the beach, you can use fresh seaweed (rinse with tap water), chop seaweed and dig it into the soil around plants. The seaweed adds nitrogen, potassium and other trace minerals to soil.
Compost or Manure Tea
Another organic alternative is to make a "tea" to use as fertilizer. Fill a bucket one-third full with compost or manure, then fill to the top with water. Mix well, and let sit for one to four days. Pour the tea directly around hibiscus plants. You can make more tea by filling the bucket with water again.
Chemical or nonorganic fertilizers such as TruGreen or Growmore (as well as other brands) comes in both powder and liquid form. The fertilizers are engineered to add phosphates, nitrogen and potassium to soil, which benefit hibiscus plants. You can purchase chemical fertilizers at garden centers.