Landscape plants stressed because of low fertility levels are also more susceptible to insect, disease, and other problems such as lack of hardiness. The presence of many dead twigs or branch tips also may indicate the need for feeding. However, these symptoms also may be caused by many environmental, insect, disease, and other cultural problems. It would be prudent to rule out any such causes before automatically embarking on a fertilization program. Having your soil tested by a reputable laboratory could be helpful in determining actual soil fertility levels.
Fertilizers can be expensive and are manufactured using nonrenewable fossil fuels.
Potentially they can enter water supplies if heavy leaching and erosion occur. It is important to fertilize woody plants only when needed, to apply reasonably precise amounts of fertilizers at the correct times, and to place fertilizers where they are available to the roots. Whether or not you carry out a regular yearly fertilizer maintenance program for landscape plants should depend on the inherent fertility of the soil and how well the plants are growing. Very sandy soils lacking sufficient clay and organic matter are quite prone to nutrient deficiency. Landscape plants in such soils often exhibit deficiency symptoms without a regular fertilizer maintenance program.