Growing Degree Day (GDD) Summary, May 2024

The Plant Phenology and Growing Degree Day (GDD) posts and impacts have been a Buckeye Yard and Garden onLine (BYGL) staple for years. GDD will continue to be an important part of the blog written to assist green industry professionals, Extension professionals, Extension volunteers, and people with a passion for plants and pests too.

Readers will continue to see those updates in the BYGL on a monthly basis, but there is no better way to track GDD and ultimately the plant blooms and insect activity on your own. Be sure to save this website ( https://weather.cfaes.osu.edu/gdd/default.asp ) as a favorite, and set those calendar reminders now to check the website regularly.  

Here is a Growing Degree Day Refresher if GDD is new, or you need a little review!

GDD are a measurement of the growth and development of plants and insects during the growing season. Development does not occur at this time unless the temperature is above a minimum threshold value (base temperature). The base temperature varies for different organisms. It is determined through research and experimentation. The actual temperature experienced by an organism is influenced by several factors. These factors affect growth and development. For instance, depending on the weather, an organism's temperature may be a few degrees more or less than that recorded. An organism may spend its time in the shade or under direct sunlight. The fertility and nutrient content of the soil directly affect the growth rate of plants and thereby indirectly influence insect growth rates. The presence of weeds and precipitation may indirectly influence development. Due to these factors and some other scientific considerations, a base temperature of 50 degrees Fahrenheit is considered acceptable for all plants and insects. (Source: OSU Plant Phenology Website)

The one thing that we do know is that the sequence of events – both plant and pest development – consistently occurs in the same order no matter the weather.   

At the end of each month this calendar year, there will be a GDD Summary Alert Posted to BYGL. While today's post has some areas seeing zeros - it is the start of the calendar year – we will have to see if that is true. As you can see below, 21 Ohio locations (City, County, and Zip Code) have been chosen across the state and will continue to be used for the monthly updates. 

Not seeing your city or zip code? No worries! You can always check out the website, type in your Ohio zip code, and ground truth what you are seeing with what the calendar says should be occurring. 

Additionally, once you are at the website, you can click on summary and it will provide you the yearly GDDs and the 20 year average. To illustrate that, I have done this with the zip code at my office (43615) in Toledo, Ohio using May 31 as the common date. 

20 Year GDD Average for Toledo (43615) on May 31 - 600 GDD Units