Annually, St. Lucie County, like many other counties in Florida, prohibits fertilizer applications from June 1 through September 30. Florida receives approximately 53 inches of rainfall each year, with most of it falling during this period. Fertilizer restrictions are intended to minimize nonpoint-source pollution of groundwater and surface water caused by fertilizer leaching and runoff.
Although we are permitted to fertilize our lawns and landscapes outside of the restricted period, we should remain mindful of the need to protect our water resources year-round. Follow UF/IFAS nitrogen fertilizer recommendations: apply 1 pound of slow-release nitrogen per 1,000 square feet or 0.5 pound of quick-release nitrogen per 1,000 square feet. If you are unsure how to calculate the proper fertilizer rate, contact your local UF/IFAS Extension office.
Applying more than the recommended rate can cause excess fertilizer to enter waterways and negatively impact water quality. UF/IFAS Extension recommends using fertilizers containing at least 30% slow-release nitrogen. The fertilizer bag label will indicate the percentage of slow-release nitrogen in the product.
Do not fertilize your lawn if rain is forecast within the next 24 hours. Although rainfall can help dissolve fertilizer so plant roots can absorb it, excessive rain can cause fertilizer to run off or leach away. After applying fertilizer, lightly irrigate the turf. Excessive watering can dissolve the fertilizer too quickly and move it out of the root zone, where it is needed. Fertilizer should also never be applied to saturated soil, as this can contribute to water pollution.
Before resuming a fertilizer program, consider verticutting the lawn. Verticutting removes thatch, an unwanted layer of organic matter that accumulates between the grass blades and the soil surface. This layer consists primarily of grass clippings, stolons, and other plant material. Excessive thatch can prevent fertilizers and pesticides from reaching the roots and can reduce the amount of oxygen and water available to the turf.
Implementing an effective fertilizer program before the next fertilizer ban begins on June 1 is essential. After the ban ends, fertilizer applications during the first week of October, March, and May can greatly benefit the turf. In St. Lucie County, I do not recommend fertilizing in November, December, January, or February. During these months, soil temperatures may be low, and plant roots may not be actively growing and may not be able to absorb nutrients effectively. Any fertilizer particles not taken up by the roots may leach through the soil or run off into surface water.
Preventing and controlling winter’s annual weeds should also be a priority in the landscape. Applying pre-emergence herbicide between mid-September and the first week of October can help prevent winter annual weeds from becoming established. If winter weeds are left uncontrolled, they will die in the spring and summer, leaving open spaces in the lawn. Summer annual weeds can then occupy these bare areas, creating a recurring cycle of weed infestation.
For more information about horticulture-related topics, contact Grantly Ricketts with UF/IFAS Extension at gricketts@ufl.edu or 772-462-1660.
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