The correct spreader setting for grass seed is not a single number but a variable unique to the specific seed, the spreader model, and the desired application rate. Manufacturer setting charts are often calibrated for granular fertilizer, which can lead to wasteful over-seeding or patchy, thin turf growth. Grass seed varies widely in size, weight, and flow characteristics compared to fertilizer pellets, meaning a setting that works for one product will not work for another. To achieve a dense, uniform stand of grass, you must determine the precise setting for your equipment through a calibration process.
Understanding Seed Rate and Spreader Types
The foundation of successful seeding is knowing the target density, defined by the seed rate, typically measured in pounds per 1,000 square feet. This rate is usually found directly on the bag of grass seed and can range significantly based on the species and the project goal. Applying too little seed results in bare patches and increased weed competition. Applying too much causes seedlings to compete for limited resources, leading to weak, leggy growth.
The spreader type fundamentally changes how the seed is dispersed and how the setting is determined. Drop spreaders release the seed directly beneath the hopper in a fixed strip, offering high precision for small areas and near flower beds. Rotary, or broadcast, spreaders use a spinning disk to fling the seed in a wide arc, making them faster and more efficient for large lawns. The rotary spreader’s application width is variable and affected by walking speed, whereas the drop spreader’s width is fixed.
The Calibration Process
Since no universal chart exists, calibrating your spreader is the most reliable way to achieve the correct application rate. The goal is to find the dial setting that releases the required weight of seed over a measured area. Begin by measuring a test area, such as 100 square feet; this simplifies the math since the target rate per 100 square feet is one-tenth of the rate per 1,000 square feet.
Weigh out a known amount of seed and load it into the spreader hopper. Select a starting setting on the spreader dial, which can be an educated guess or a low-to-mid-range number suggested for granular products. Conduct the test on a smooth surface like a driveway or tarp so the dispersed seed can be easily collected.
Walk the measured test area at a consistent pace, engaging the spreader mechanism at the start and disengaging it at the end of the boundary. Weigh the remaining seed in the hopper and subtract this from the initial weight to determine the exact amount dispersed over 100 square feet. If this dispersed weight is too high or too low, adjust the spreader setting and repeat the test until the output matches the desired rate. Documenting this final setting is important, as it is specific to that bag of seed and that particular spreader.
Application Technique for Uniform Coverage
Once the correct setting has been determined, the application technique must be precise to maintain uniform coverage across the entire lawn. Maintaining a consistent walking speed is important, especially with rotary spreaders, because the pace directly affects the width and density of the seed distribution. Any variation in speed can lead to streaks of over- or under-applied seed.
The most effective strategy for uniform coverage is to apply the seed in two perpendicular passes, which is often called a half-rate application. Calibrate your spreader to release half of the total target rate. Spread the entire area once traveling north-south, and a second time traveling east-west. This dual-pass method minimizes the risk of missed spots and ensures a more even distribution of seeds across the soil surface.
When using a drop spreader, each pass must slightly overlap the wheel track of the previous pass to prevent untreated strips. For rotary spreaders, the effective spread pattern requires overlapping the edge of the current pass with the farthest reach of the previous pass. To avoid dumping piles of seed at the ends of the lawn, the spreader gate should be closed before stopping or turning, and opened only after the walking motion has begun again.