Trees have nutritional needs that may not be met in urban landscapes. A soil or foliar analysis can determine what nutrients are lacking. Fertilizer is not always the solution and other causes like poor planning or lack of education should be investigated first. There are different types of fertilizers like complete, organic, inorganic, slow-release, and controlled-release. Slow-release fertilizers contain nutrients that delay initial availability or extend it over time to reduce leaching and burning, while controlled-release nutrients are released at a specific rate over a set period. Water-insoluble nitrogen defines many slow-release fertilizers.