Photo courtesy of Washington State Department of Ecology.

If you are planning to fertilize your yard this spring, make sure that you use the right type of fertilizer and don't apply more than is necessary.  Fertilizer runoff contributes to nutrient pollution and the harmful toxic algal blooms that frequently occur in the St. Johns River each summer.

  1. Always begin by determining the appropriate time of year and frequency to apply fertilizers.  You generally don't want to fertilize during the winter months when turfgrasses are dormant.  For St. Augustine grass, you may only need to fertilize two times a year, during the growing season in March and September.  We recommend that you try to avoid applying fertilizers during the summer rainy season, when fertilizers are more likely to run off into waterways as a result of heavy rains.  To green your lawn, simply apply iron (Fe) during the month of June.  Alternative groundcovers like Bahia grass & Perennial Peanut require little to no fertilizer. 
  2.  Next, make sure that you carefully measure your yard to determine the square footage and the amount of fertilizer that you will need.  Here is a website from the South Florida Water Management District that will help you with your calculations. 
  3. Now it is time to go shopping.  Select a fertilizer that is low or no phosphorous and contains 50% or more of the nitrogen in a slow-release form.  If you can’t find one with 50% or more slow-release nitrogen, select the fertilizer with the highest percentage available.  Do not buy fertilizers that contain weed killers.  This is often easier said than done.  Unfortunately, many retailers do not carry a wide selection of slow-release fertilizer products.  However, this situation can be remedied if we, the consumers, make sure to ask garden centers to carry low phosphorous, slow-release fertilizers and we purchase them when they do.  Check the chart on our River Friendly Fertilizing page to find fertilizers that contain 50% or more slow-release nitrogen.  Locally, Lowe's is test marketing an organic slow-release fertilizer from Jungle Growth that meets the 50% criteria, and many of the Ace Hardware stores carry Green Edge, an organic fertilizer made from JEA biosolids. 
  4. Use only the amount of fertilizer that is necessary for the size of your yard.  Too much fertilizer can actually weaken your lawn, making it more susceptible to pests, weeds, and disease.  When using a 50% or more slow-release fertilizer, you can apply up to 1 lb. of nitrogen per 1,000 square feet.   Follow the instructions on the bag.  You can also verify the correct amount by applying a simple equation. To calculate the amount of fertilizer to apply to ensure the right amount of nitrogen:
    (100 ÷ % of nitrogen in fertilizer bag) x (square footage ÷ 1,000) = lbs. of fertilizer to apply
    Example: (100 ÷16) x (1,500 ÷1,000) = 9.375
  5. Use fertilizer responsibly.  Never apply before heavy rain is expected.  Do not fertilize adjacent to waterways, leaving a "ring of responsibility" of approximately 10 feet.  Clean up any fertilizer that accidently spills or falls on the driveways, sidewalks, or roads. 

You may also want to consider reducing the size of your lawn by expanding or creating beds with native or drought-tolerant plants and trees.  The benefits include:

  • Beds can create buffers to help prevent runoff and keep fertilizers and chemicals on your lawn.
  • Native or drought-tolerant plants that are appropriate for the conditions in your yard (soil type, amount of sunlight, etc.) often require little to no irrigation and fertilizer once established, saving you money and time.  
  • Native plants and trees can provide valuable habitat for wildlife, attracting birds and butterflies to your yard.
  • Trees help reduce the volume and slow the flow of stormwater. Trees are natural pollution filters, removing nutrients, like nitrogen, and other pollutants from stormwater. Trees also improve air quality, and reduce energy consumption by shading and cooling our homes and businesses.