Fertilizer response varies with the plant as well as the environment. Soil fertility, aeration, drainage, exposure to sun and wind, temperature of the site, and proximity to buildings, walks, and streets are but a few of the many factors that influence plant growth. Best growth depends upon the landscape use of the plant. The largest plant is not necessarily the best.
Fertilizer comes second to water in producing color and size, two attributes of good growth.
The extent to which fertilizers are applied for established plants depends upon the fertility of the soil and the growth desired. If plants are growing well and look good, you may choose not to add more fertilizer. For additional growth, more fertilizer would be added. This is also true where malnutrition is evident, as indicated by poor foliage color and short and weak growth not caused by lack of moisture or fungus or insect attack. They come from the soil and from applied nutrients.