Grower Degree Days Calculator Grower Degree Days is a heat index calculation that helps growers determine all sorts of useful information: Bud swell, leaf emergence, flowers, and pest emergence to name a few. In the nursery industry this gives us an opportunity to better plan and be successful with our pest management plans. Insects and mites are cold blooded, so they rely on certain thresholds of temperature for them to become active. Grower Degree Days Calculator Zip Code Date Calculate GDD ---- High/Low--°F / --°F The Basic Way to Calculate Degree Days Is This Using this equation will give you the number of degree days you accumulated for your area each day. This can be done every day to give you a running total for the year. Need to Schedule a Plant Pick Up? Contact us with your plant needs and we’ll work with you to generate an order. Contact Us Today Join 1000+ landscapers and business owners to receive the latest news and updates from the Goodmark team! Sign Me Up!