Updated Nov 30, 2023
Growing Degree Days (GDD) is a thermal, time measurement that allows us to track the intervening time between critical growth stages. GDD is calculated by taking the average of the high and low temperature in C for each day with a base temperature of 0 C. ( temperatures calculated below 0 do not count)
It takes 130 GDD for emergence to take place from a 1 inch planting depth. The emergence of leaves on the main stem takes 90 to 100 GDD for each leaf. Wheat planted on Sept 15 (795 GDD to date) should have close to 5 - 6 leaves on the main stem. Plants that have produced tillers, the Growth Stage is Zadoks 2.0. If a plant has 3 tillers it is at growth stage 2.3. On Jan 1st we reset the GDD accumulation to zero. After an accumulation of 250 to 300 GDD we should begin to see green up. That marks the GS to determine nitrogen rates and timing of applications. Wheat is a base 0 C degree crop which means when daily temperature is above zero the plant will begin to grow.