Seashore Paspalum at mowing heights above 9mm have repeatedly provided uneven fall overseed turf stands and a discontinuous surface into even late spring. A strip plot field design experiment was conducted to evaluate the effect of gibberillic acid rates (0, 5, 10, 20, 40, 50, 100, 150 and 200 ppm). After GA was applied, three mechanical overseed preparations: P1 (turf mowed back to 16, then 9, and then 8mm), P2 (turf mowed back to 16mm), and P3 (turf mowed back to 16mm, and lightly vertically mowed). Plots were overseeded at 700kg/hectore and scored monthly for percent plot overseed cover, and turfgrass quality. When averaged over mechanical treatments, there was no difference in percent ryegrass overseed cover in November or December. After emergence, all treatment combinations of (GA x P) for percent ryegrass cover were lowest = (P2), middle = (P3) and greatest for (P1). Among (P1) turfs, percent plot cover decreased at 100ppm and above, soon after emergence. GA levels of 5 to 20 ppm had large amounts of straw present (22-26%). The amount of straw present decreased greatly at 50 ppm GA, or greater.  The 50 ppm GA level was the only level to have initial quality (6.7) immediately after ryegrass emergence. When observed across seasonal observation dates, the 50 ppm GA level produced fully acceptable turfgrass density scores across all three mechanical preparatory treatments, and were much better in quality than 0 ppm GA, in December and January. Without GA, turfgrass quality was quite low in December and January, which did improve until Feb (for P2, or P3 plots), or until March (P2).  Certain applied GA levels improved overseed performance.