New Year Brings Beginning of the 2023 Plant Phenology and Growing Degree Day Calendar

Published on

A staple in the Buckeye Yard and Garden Line (BYGL), The Plant Phenology and Growing Degree Day Posts will continue to be a part of this year's Alerts. While there isn't a lot to report, the value of today's post shows that no matter where in Ohio you are from north to south, or east to west, we all begin at zero. 


As temperatures warm, we will begin accumulating growing degree day (GDD) units. You will see those updates in the BYGL, 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 ( ) 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 insects and plants. 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)


At the end of each month this calendar year, there will be a GDD Summary Alert Posted to BYGL. While today's post has everyone seeing zeros - it is the start of the calendar year. As you can see below, 20 Ohio locations (City, County, and Zip Code) have been chosen across the state and will continue to be used for the monthly updates. 


GGD Chart, January 1, 2023


Ohio City (County) Zip Code    GDD Unit Accumulation 
Bryan (Williams) 43506 0
Toledo (Lucas) 43615 0
Sandusky (Erie) 44870 0
Elyria (Lorain) 44035 0
Barton (Geauga) 44021 0
Jefferson (Ashtabula) 44047 0
Van Wert (Van Wert) 45891 0
Findlay (Hancock) 45840 0
Medina (Medina) 44256 0
Mt. Gilead (Morrow) 43338 0
Mt. Vernon (Knox) 43050 0
Steubenville (Jefferson) 43952 0
Dayton (Montgomery) 45417 0
Springfield (Clark) 45505 0
Columbus (Franklin) 43210 0
Lancaster (Fairfield) 43130  0
Marietta (Washington) 45750 0
Cincinnati (Hamilton) 45223 0
Hillsboro (Highland)  45133 0
Ironton (Lawrence) 45638 0


Not seeing your city or zip code? No worries! You can always check out the website and type in your Ohio zip code.