The main soil nutrients that support bloom in plants are somewhat different or used in different ratios that those that tend to support foliage and root growth. In general terms nitrogen rich fertilizer supports healthy foliage growth while potassium underpins root health and flower development. Phosphorous plays a role by encouraging abundant blooming and fruiting in plants, shrubs and trees. Fertilizers that contain both macro and micro nutrients can round out the nutritional support of plants and are a bonus in any formulation.
Espoma's organic line of Tone fertilizers are widely used to induce bloom in a range of plants and specialty Tones are blended for use on roses, bulbs, flowering trees, fruit trees, annuals, perennials and acid loving plants. Espoma products contain macro and micro-nutrinets derived from a range of organic sources including kelp, fish emulsion, potash, bone meal, greensand, manure, magnesium and beneficial microbes.
Synthetic complete fertilizers with a relatively low nitrogen content and relatively high phosphorous content are ideal to boost flowering in most plants. Excess nitrogen will drive foliage growth at the expense of flowering and should be avoided when trying to encourage flowering. Scotts Bloom Booster is a slow release formulation with a guaranteed analysis of 10-16-10. Choose chemical fertilizers with a higher middle number in their formulations to encourage blooming.
Acid Rich Fertilizers
Many flowering plants including gardenias, azaleas, rhododendrons, magnolias, camellias and dogwoods thrive in acid rich soil sand benefit from acid rich fertilizers. A widely available and proprietary formulation is Scotts MirAcid is water soluble complete fertilizer formula with a guaranteed analysis of 30-10-10.