Landscape Best Management Practices

Before You Buy That Bag of Fertilizer


Fertilizing your lawn is part of a great American pastime, just like watching the big game or barbecuing on the weekends. However, unlike football and barbecue, improper fertilization of your lawn can cause negative environmental impacts to our water quality, plants, and animals. If we apply too much fertilizer, it can wash off our lawns and into our waterways, causing nuisance plants to grow, harming fish and animals, and requiring water managers to apply costly chemicals to control aquatic plant growth.

Before you buy that bag of fertilizer, consider the following misconceptions that many people have about fertilizing their lawns.

Misconception One: Higher Numbers Make a Better Fertilizer


Some people believe that the higher the three numbers on a fertilizer bag are, the better the fertilizer will be for their lawn. Actually, the three numbers represent the fertilizer's nutrient concentration in percentile form. For example, a bag labeled 20-5-25 means that it has 20% nitrogen, 5% phosphorus, and 25% potassium. Depending on the brand, the rest of the fertilizer might contain minor nutrients and filler material.

Excessive nutrients have been shown to cause numerous water quality problems in our canals and ponds, problems that may find their way to the Everglades and our nearby reefs. Phosphorus is found naturally in South Florida soils, so your lawn doesn't really require extra amounts. When you buy fertilizer, look for the number in the middle, making sure it is two or less. Always remember that for lawn fertilizer, 2% phosphorus or less is best!

Misconception Two: Lawns Should Be Fertilized Once a Month


Lawns should only be fertilized as needed. Also, you should never apply fertilizer prior to a major rain event because the precipitation will wash the fertilizer past the root zone before it can be absorbed by the grass.

The most effective time to fertilize the lawn is prior to the rainy season, which is between June and November. The months of March and October are ideal for fertilization. March is the beginning of growing season, and October fertilization allows for proper nutrition during the dry season.

These are just two of many misconceptions about fertilization. For more information, contact the Natural Resources Planning and Management Division at (954) 519-1222.