Primo Maxx GDD calculator guide

Cornell Turfgrass Program explains that temperature affects the length of the suppression phase after Primo Maxx applications. As air temperatures increase, turf breaks down PGRs faster, which makes fixed calendar intervals less efficient during the growing season.

Lawn Dominator tracks PGR timing with Celsius-scale GDD. Cool-season trinexapac sessions use a 0°C base, while warm-season trinexapac sessions use a 10°C base. The app and web calculator may display Fahrenheit weather, but the PGR math converts the daily high and low to Celsius before applying the base. Neither threshold replaces the product label, turf species sensitivity, mowing height, rate, weather stress, or local regulations. Treat GDD as a tracking model, not a universal prescription.

• Cornell Turfgrass Program: cool-season trinexapac research context
• Reasor et al. 2018, Crop Science: warm-season bermuda PGR modeling context

• Open the GDD Calculator.
• Use the from-date calculator starting on your last PGR application date.
• Log the product, rate, weather, mowing response, and next target in the Lawn Dominator app.