Many trees and landscape plants require little or no fertilizer once they are established and mature. In fact, fertilizers can be hazardous to the health of your yard and the environment when they are misused.
When over-applied, fertilizers may aggravate insect and disease problems and force excessive growth which must be mowed or pruned. Excess fertilizers can run off yards into waterways or seep into aquifers, polluting drinking water.
The decision to fertilize should be based upon the health of the plant, the desired rate of growth, and a soil analysis. A soil analysis will tell you the soil pH and the amounts of nutrients in the soil that are available for plant growth. Soil pH affects the availability of nutrients in the soil. When you choose the fertilizer to use, it should have an analysis, which provides the nutrients that are lacking in the soil.
What is a slow-release fertilizer?
Slow-release fertilizers release nutrients to plants slowly, over an extended period or time. You may see slow-release fertilizers labeled as extended-release. When fertilizer nutrients are in "slow release" forms, they are available to plants over a longer period of time and fewer nutrients are wasted or lost as pollutants.
Is organic fertilizer better than non-organic?
Organic fertilizers come from plant or animal sources and can be less likely to “burn” or injure plants. Organic fertilizers, such as fish emulsion, are still fertilizers, so be cautious when using them. The "100% Organic" claim often refers only to the nitrogen in the bag. Furthermore, the nitrogen can be derived from natural products such as manure or it can be from synthetic chemicals such as urea. Read the label to determine where the "organic" nitrogen is coming from.
How do I know if it’s time to apply fertilizer?
Look for vegetation showing signs of poor growth, poorly colored leaves (pale green to yellow), leaf size smaller than normal, earlier than normal fall coloring and leaf drop, twig or branch dieback, or little annual twig growth. The method to use when applying fertilizer depends on the type of fertilizer and the plant’s needs. Your soil type will determine how often you should apply fertilizer. Consult your soil test report.
Fertilizer is not plant food. Symptoms of poor growth are not always related to low levels of nutrients in the soil. Poor plant growth can be due to heavily compacted soil, stress induced by insects, diseases, and weeds, or dramatic weather conditions, such as drought.
Let the plant be your guide! Don’t assume fertilizers will automatically cure your plant problems. Before fertilizing, determine the cause of the problem and try to correct it.