Fertilizer is the most-purchased and least-understood category in residential landscape care. Florida's combination of sandy soils, heavy rainfall, and aggressive marketing creates a perfect environment for the wrong product being sold at the wrong rate to the wrong yard. Here are the five myths we hear most.
Myth 1: 'More fertilizer means greener plants.'
No. Plants take up nutrients within a narrow range; beyond that, excess fertilizer either leaches into groundwater (nitrogen) or accumulates in the soil to toxic levels (phosphorus, salts). Past the optimum, the next pound of fertilizer is doing harm.
Many counties in Florida now have summer fertilizer restrictions specifically because of nitrogen runoff into impaired waterways. The restriction is not anti-lawn; it is anti-pollution.
Myth 2: '10-10-10 is a good general-purpose fertilizer.'
Balanced NPK ratios assume the soil is deficient in all three macronutrients in equal proportion. Florida sandy soils are typically nitrogen-deficient, potassium-deficient, and phosphorus-sufficient (often excess from decades of over-application). A 15-0-15 or 16-0-8 is closer to what most established Florida landscapes actually need.
The only way to know for sure is a soil test. Without one you are guessing.
Myth 3: 'Fertilizer fixes yellow leaves.'
Yellow leaves can mean a dozen things. Iron chlorosis (yellow with green veins, often on new growth) means pH is too high — fertilizer won't fix that, sulfur amendment will. Magnesium deficiency (yellow on older leaves with green inverted-V) needs Epsom salts or dolomitic lime. Nitrogen deficiency (uniform pale green) does respond to fertilizer, but is only one of many causes.
Diagnose first. Fertilize second.
Myth 4: 'Trees need annual feeding.'
Most mature trees in a typical residential landscape are getting plenty of nutrients from lawn fertilizer, leaf litter, and natural soil mineralization. Routine tree fertilization without a confirmed deficiency is, in most cases, money spent for no benefit. Where trees do benefit from supplemental fertilization, the application should be a deep-root injection of a slow-release formulation, not surface granular.
Myth 5: 'Spike fertilizers work.'
The driven-in 'tree spike' delivers a high-concentration salt slug to a one-square-foot area of root zone. Trees do not have roots in that geometry; their feeder roots are spread across the entire dripline, mostly in the top 12 inches of soil. Spikes are convenient retail packaging, not effective horticulture.