The Summer Shift: From Fertilizing Plants to Feeding Soil 

By Sidney Craig

Every summer, Tampa Bay enters an intense season of high temperatures, rain, thunderstorms, and occasional hurricanes. From June 1 through September 30, Pinellas County, and many others, prohibit the sale and use of lawn and landscape fertilizers containing nitrogen or phosphorus. This does not mean summer gardens have to go hungry, but it does mean we need to shift from fast, soluble nutrients to caring for the soil system itself. The ordinance exists because most, if not all, of Florida is connected to our waterways in some way.

When fertilizer is applied incorrectly or before heavy rain, it can wash from lawns into storm drains, which lead directly to local waterways. Rain that falls on roofs, driveways, lawns, sidewalks, streets, and planting beds has two basic paths: soaking into the ground or across the surface as stormwater runoff. Once that runoff reaches a storm drain, it does not go to a sewage treatment plant. It moves through a separate stormwater system and drains toward nearby ponds, canals, creeks, bays, and the Gulf. 

The fertilizer ban doesn’t mean you can’t take care of your plant health. Summer fertilizer alternatives focus on soil health and targeted nutrition instead of restricted nitrogen and phosphorus. Pinellas County still allows the sale of composts, macronutrients such as potassium, sulfur, calcium, and magnesium, and micronutrients such as iron and manganese. At the heart of summer plant care is more attention to soil structure, organic matter, root health, and minor elements. 

What Leaves the Yard Doesn’t Leave the Watershed 

Any loose material in the landscape can travel with the water runoff. Fertilizer granules left on a driveway, grass clippings in the street, soil from an eroding bed, or dissolved nutrients from a recently fertilized lawn can all be picked up during a summer storm. Even fertilizer applied carefully to turf or landscape beds can become a problem if heavy rain moves it before plants have time to use it. This is one reason the ordinance focuses so strongly on timing. During the rainy season, the distance between your yard and the bay can become very short. 

Leaching is another pathway for rain water. In much of Florida, including Pinellas, soils are sandy. Sandy soils have large pore spaces, which means water can move through them quickly. That is useful when we need drainage, but it also means a heavy summer rain can push water below the active root zone before roots have time to take up the nutrients dissolved in it. A heavier clay or loam soil has more small particles and more surfaces that can hold nutrients. Sandy soil has fewer of those holding sites. Florida soils are often low in organic matter as well, which further limits their ability to store water and nutrients. In practical terms, this means that a quick-release fertilizer applied during the rainy season may not stay where the plant needs it. Some of it may move downward through the soil. Some of it may move sideways with runoff. Either way, the plant food can become part of the watershed, literally washing your plant’s food and your money down the drain. 

 Nitrogen is especially mobile. In its nitrate form, nitrogen dissolves easily in water and moves wherever that water moves. Picture stirring sugar into a glass of water: once dissolved, it no longer sits in one place, it moves with the water. Phosphorus, on the other hand, behaves differently because it can bind to soil minerals, but sandy, low-organic-matter soils may have limited capacity to hold it, especially when phosphorus is overapplied or carried off with runoff. That is why the Pinellas ordinance restricts phosphorus unless a soil test shows it is needed. 

The issue is not only what we apply, but whether our soil can hold it long enough for roots to use it. Once nitrogen and phosphorus reach ponds, canals, creeks, Tampa Bay, or the Gulf, they do the same thing they do in a garden: they feed plant growth. The problem is that algae are plants too. A small amount of algae is normal and necessary; algae and phytoplankton form part of the base of aquatic food webs. But when too many nutrients enter the water, algae can grow faster than the system can handle. This over-enrichment is called eutrophication. 

Eutrophication is the aquatic version of overfeeding. Add too much nitrogen or phosphorus, and algae can multiply rapidly. The water may turn greener, browner, murkier, or smellier until sunlight has a harder time reaching underwater plants. In Tampa Bay, this is a key issue because seagrasses need clear water. They are flowering plants, not seaweed, and they photosynthesize just like land plants do. If algae clouds the water, sunlight cannot reach the blades.

When seagrasses decline, the effects move through the whole bay. Seagrass beds provide nursery habitat for fish and invertebrates, shelter for small marine life, food resources for animals such as manatees, and stabilization of sediments. They help hold the bottom in place and keep the water clearer. A loss of seagrass is not just a loss of plants; it is a loss of habitat, structure, and overall ecosystem resilience. 

Algal blooms can also affect oxygen. When algae die, bacteria and other decomposers break them down. That decomposition uses dissolved oxygen in the water. If enough oxygen is consumed, fish, crabs, shrimp, and other aquatic animals can become stressed or die. This is how excess plant food can lead to dead zones and fish kills. The nutrients begin as something familiar to gardeners, but once they leave the yard, they can feed a chain of problems downstream. 

Bay-Friendly Summer Plant Care 

There are many ways to improve soil and plant health without the use of fertilizers. First, use soil amendments to add nutrients, improve water retention, and add beneficial microbes. The next step is to identify specific deficiencies in your plants. Yellowing can come from many causes other than nitrogen deficiency including too much water or too little water, root damage, high pH, salt stress, disease, insect pressure, or micronutrient deficiency. This is especially true in palms and ornamentals, where iron, manganese, magnesium, zinc, copper, sulfur, or boron may be part of the problem. Targeted minor-element products or soil acidifiers are often more appropriate than broad fertilizer.

In summer, the goal is not to replace one kind of overfeeding with another. The goal is to garden with the watershed in mind. A careful gardener sends less downstream. That is good for the yard, good for the bay, and good for the living edge between them.

Soil Improvement Products

 Our first recommendation is often the least flashy one: compost. Black Kow or Mushroom Compost feeds plants while improving the storage system around the roots. In sandy soil, compost adds organic matter, helps the soil hold moisture, supports microbial life, and improves the soil’s ability to retain nutrients instead of letting them wash through after every heavy rain. For beds, vegetables, herbs, annuals, perennials, and new planting areas, compost is a foundation. It works slowly, but it changes the conditions in which the roots are living. 

Worm castings work in a similar but gentler way than fertilizer. They are useful when a plant needs mild support rather than a strong push. In containers, vegetable starts, herbs, annuals, and sensitive plantings, worm castings can be mixed into the soil or used as a light topdressing. They add organic matter and biological activity close to the root zone. In a Pinellas summer, that matters. Rather than forcing quick growth with soluble nutrients, worm castings help the plant work with the soil it already has. 

For broader soil-building, we offer COMAND Lawn & Turf compost. It provides organic matter and beneficial microbes that support healthier soil biology, improve moisture retention, and help rebuild the physical and biological structure of depleted soil. That makes it especially useful in sandy landscapes where water and nutrients often move too quickly. A soil that holds moisture longer is easier on plants, easier on irrigation, and less likely to send excess nutrients away from the root zone during summer storms.

Many plants do not thrive if the soil pH is too high. Espoma Soil Acidifier to make the soil more acidic.  Because soil pH affects nutrient availability, a nutrient can be present in the soil but still unavailable to the plant.

Targeted Plant Support Products

For general micronutrient support, we carry Southern Ag’s Essential Minor Elements Mix. This is the product to consider when plants appear to need mineral correction rather than general nitrogen feeding. It is especially useful when the goal is to address the small but necessary nutrients that Florida soils and Florida pH conditions can make difficult for plants to access. 

For palms, we offer Southern Ag Palm Nutritional Spray. Palms are not broadleaf trees, and they often show nutrient stress in specific ways: yellowing, browning, curling, weak new growth, or injury in the spear and newest leaves. Palm Nutritional Spray contains manganese, magnesium, iron, and sulfur and is labeled for palms and other ornamentals to help prevent or correct nutritional deficiencies. Manganese is especially important in palms because severe deficiency can damage new growth. 

For more general ornamental and garden use, we carry Southern Ag’s Garden Nutritional Spray. This is a chelated micronutrient spray containing iron, manganese, zinc, magnesium, copper, and sulfur. “Chelated” means the nutrients are bound in a form that can help keep them more available to plants, especially when soil conditions make uptake difficult. This can be useful for yellowing foliage on ornamentals, shrubs, vegetables, and other garden plants where micronutrients are more likely to be the issue than nitrogen.