You will find that some fertilizers are described as being designed for certain types of plants. Rhododendron and azalea food and rose food are two of the more common. Since these plants are acid-soil lovers, these fertilizers will help these plants thrive in soil that may be slightly alkaline or neutral. Don't let that lead you into believing that acid-loving plants will live in an alkaline soil. Since most desert and arid areas have highly alkaline soils, these plants cannot live there, even with the addition of these nutrients.
There are other types of special purpose fertilizers. Several brands tout the ability to promote blooming for vegetables and ornamentals. The fact is that these fertilizers contain high amounts of phosphorus. Plants do need phosphorus to bloom, but the addition of high levels of phosphorus does not guarantee increased blooms.
