By Pam Brown, Urban Horticulture Extension Agent
When you start seeing new green leaves on landscape plants or your grass is beginning to grow, it is time for spring fertilizing. At the most basic level, fertilizers provide nutrients that help plants grow better. You can fertilize by applying compost, a packaged commercial fertilizer or a specific mineral, such as iron. Lawns, woody landscape plants and palms benefit from different fertilizer blends, so I encourage you to review the linked University of Florida/IFAS publications listed below for specifics.
When selecting fertilizer, you will see three numbers listed on the bag like 15-0-15 or 16-2-8. The first number is the percent of Nitrogen contained in the bag, the second number is the percent Phosphorus and the third is Potassium. You will want to look for slow-release fertilizers or at least fertilizers with a high percentage of slow-release nitrogen in them. Nitrogen promotes shoot growth, so if you use slow-release nitrogen, you will have less of a succulent new growth surge. Using slow-release fertilizers can lead to less insect problems for both lawns and landscape plants since insects are attracted to the tender new growth. Slow-release products are also less likely than 100% water soluble fertilizers to leach through the soil to ground water in heavy rain events. When looking for slow-release, other words can mean this same thing, like poly coated, sulfur coated, or water-insoluble.
Be careful when applying fertilizers, they can be a real source of pollution in our waterways, bay and gulf. It is best not to apply fertilizer if heavy rain is forecast. Using a drop spreader will help keep fertilizer away from water bodies, driveways and sidewalks. If you spill fertilizer granules, sweep them up or back up onto the lawn. Rinsing them off hard surfaces with a hose could send fertilizer down the storm drain. In the summer you can apply chelated iron or iron sulfate instead of nitrogen to green up the lawn without increasing growth. Also use caution applying “weed and feed” products. The herbicides in these products can injure some trees and shrubs.
Fertilization of Turfgrasses on Florida Soils
Fertilizer Recommendations for Landscape Plants
Fertilizing Landscape Palms in Florida Landscapes
How to Calibrate Your Fertilizer Spreader