Grass fertilizer is a formulated product designed to supplement the nutrients naturally present in the soil, helping the turfgrass grow thicker, greener, and more resilient. These products contain varying ratios of three primary macronutrients—Nitrogen (N), Phosphorus (P), and Potassium (K)—which are listed as the NPK ratio on the packaging. Nitrogen promotes the deep green color and rapid growth of the grass blades, while Phosphorus is important for strong root development and energy transfer within the plant. Potassium, often called the “stress-fighting” nutrient, helps the grass withstand environmental pressures like drought, heat, and disease. Applying fertilizer correctly is a fundamental practice that directly influences the health and appearance of a lawn, ensuring the grass receives balanced nutrition without risking damage.
Selecting the Right Fertilizer and Tools
Decoding the fertilizer label involves understanding the NPK ratio, which represents the percentage by weight of Nitrogen, Phosphorus, and Potassium. For instance, a 20-5-10 blend contains 20% nitrogen, 5% phosphate, and 10% potash. Established lawns typically require a higher percentage of nitrogen for leaf growth and a lower amount of phosphorus, unless a soil test indicates a deficiency.
Fertilizers differ based on how quickly they release nutrients, falling into quick-release or slow-release categories. Quick-release formulas are water-soluble, offering an immediate burst of nutrients that results in a rapid “green-up,” but they require more frequent application and carry a higher risk of “burning” the lawn. Slow-release fertilizers break down gradually, providing a steady, sustained supply of nutrients over several weeks or months, which promotes more even growth and reduces nutrient runoff. Many commercial products use a blend of both types.
While liquid fertilizers provide rapid nutrient absorption, granular formulations are the most common choice for do-it-yourself applications due to their cost-effectiveness and sustained nutrient delivery. Granular fertilizers require a mechanical spreader for even application. A broadcast or rotary spreader is ideal for large, open areas, as it throws the granules in a wide arc. For smaller lawns or areas requiring high precision, a drop spreader is better.
Preparing the Lawn and Calibrating the Spreader
Accurate application requires knowing the size of the area to be treated to calculate the exact amount of product needed based on the bag’s instructions. Measuring the lawn’s square footage is important, as applying too much fertilizer can damage the turf, while applying too little is ineffective. Always read the product label for specific pre-application requirements, such as whether the lawn should be dry or lightly pre-watered.
Before spreading, the equipment must be properly calibrated to ensure the correct flow rate of the granular product. Every fertilizer bag provides a recommended setting number specific to various spreader models, which controls the size of the hopper opening. Setting the spreader to this number ensures the correct amount of material, measured in pounds per 1,000 square feet, is dispersed. Use personal protective equipment, such as gloves and eye protection, before handling any granular material.
Step-by-Step Application Technique
Fill the spreader on a hard surface like a driveway or sidewalk, not on the lawn, to contain any spills that could cause localized burning. The initial pass involves creating a boundary strip by fertilizing the perimeter of the lawn first. This boundary provides a safe area for turning the spreader and prevents excessive overlapping.
The main application should use parallel passes that run in a consistent direction across the lawn. To ensure uniform coverage and avoid distinct stripes of under- or over-fertilized grass, set the spreader to half the recommended rate. With this half-rate setting, the entire lawn is treated twice, with the second set of passes running perpendicular to the first, creating a grid pattern.
Maintain a steady walking pace, as slowing down causes a heavier release of material, while speeding up results in a lighter application. Shut off the flow of granules every time the spreader stops or turns, preventing clumping and over-application. When working on slopes, apply horizontally across the grade to minimize the risk of granules washing away.
Post-Application Procedures and Seasonal Timing
Immediately following the application of granular fertilizer, water the lawn thoroughly unless the product label advises otherwise. This initial watering washes the granules off the grass blades to prevent burning and dissolves the fertilizer so nutrients can move into the soil and reach the roots. A light, even watering of about 15 to 30 minutes is sufficient to activate the product.
Any stray granules on hard surfaces like driveways or sidewalks must be swept back onto the lawn or into the dirt. Leaving fertilizer on pavement risks the material washing into storm drains, contributing to nutrient runoff. Lawn health is best maintained by adhering to a seasonal fertilization schedule, which varies based on grass type.
Seasonal Timing
The fertilization schedule varies based on grass type:
- Cool-season grasses (e.g., Kentucky bluegrass and fescue) benefit most from applications in the early fall to strengthen roots before winter, and again in the early spring to promote green-up.
- Warm-season grasses (e.g., Bermuda and Zoysia) benefit most from applications in late spring or early summer when they are actively growing, with a final light feeding in the early fall to prepare for dormancy.
Unused product should be sealed tightly in its original bag and stored in a cool, dry place to maintain its effectiveness.