@complete fertilizers sold for flowering plants (including roses and bulbs) such as 15-30-50 or 10-30-20 contain higher amounts of phosphorus (the second number) than nitrogen or potassium and are often labeled as “blossom or bloom booster”
@Fertilizers containing phosphate help stimulate plant growth, aid the development of strong roots and aid in flowering
@Scatter bone meal on top of the garden bed to add phosphorus to the soil.
@Banana peels contain nutrients that are essential for healthy potted plants. However, they don't contain everything your plant needs. As they decompose, banana peels add potassium as well as small amounts of nitrogen, phosphorus and magnesium to the soil in a similar fashion as a slow-release fertilizer.