Growing Degree Day (GDD) Summary, January 2023

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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 as promised in a January Alert (January 2, 2023). 


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, February 1, 2023


Ohio City (County) Zip Code    GDD Unit Accumulation 
Bryan (Williams) 43506 10
Toledo (Lucas) 43615 10
Sandusky (Erie) 44870 11
Elyria (Lorain) 44035 11
Burton (Geauga) 44021 10
Jefferson (Ashtabula) 44047 9
Van Wert (Van Wert) 45891 9
Findlay (Hancock) 45840 10
Medina (Medina) 44256 13
Mt. Gilead (Morrow) 43338 14
Mt. Vernon (Knox) 43050 16
Steubenville (Jefferson) 43952 16
Dayton (Montgomery) 45417 20
Springfield (Clark) 45505 20
Columbus (Franklin) 43210 17
Lancaster (Fairfield) 43130  21
Marietta (Washington) 45750 26
Cincinnati (Hamilton) 45223 29
Hillsboro (Highland)  45133 31
Ironton (Lawrence) 45638 32


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


GGD Species List (Common Name, Scientific Name, Phenological Event, GDD)


The list includes both plants and insects. Insects are bolded within the list. 


Silver Maple (Acer saccharinum), first bloom, 34; Corneliancherry Dogwood (Cornus mas), first bloom, 40; Silver Maple (Acer saccharinum), first bloom, 42; Red Maple (Acer rubrum), first bloom, 44; Speckled Alder (Alnus incana subsp. rugosa), first bloom, 52; Northern Lights Forsythia (Forsythia intermedia), first bloom, 58; Japanese Pieris (Pieris japonica), first bloom, 60; Red Maple (Acer rubrum), full bloom, 75; Star Magnolia (Magnolia stellata), first bloom, 83; White Pine Weevil (Pissodes strobi), adult emergence, 84; Border  Forsythia (Forsythia intermedia), first bloom, 86; and Eastern Tent Caterpillar (Malacosoma americanum), egg hatch, 92.