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.

They say that April showers, bring May flowers - but what will the predicted snow later this week bring, at least in the northern portion of the buckeye state? Only time will tell!

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.

GGD Chart, ending March 31, 2024

Ohio City (County)

Zip Code

GDD Unit Accumulation

Bryan (Williams)

43506

112

Toledo (Lucas)

43615

110

Sandusky (Erie)

44870

108

Elyria (Lorain)

44035

106

Cleveland (Cuyahoga)

44120

101

Burton (Geauga)

44021

97

Jefferson (Ashtabula)

44047

93

Van Wert (Van Wert)

45891

112

Findlay (Hancock)

45840

110

Medina (Medina)

44256

105

Mt. Gilead (Morrow)

43338

115

Mt. Vernon (Knox)

43050

133

Steubenville (Jefferson)

43952

130

Dayton (Montgomery)

45417

150

Springfield (Clark)

45505

150

Columbus (Franklin)

43210

159

Lancaster (Fairfield)

43130

160

Marietta (Washington)

45750

170

Cincinnati (Hamilton)

45223

168

Hillsboro (Highland)

45133

172

Ironton (Lawrence)

45638

174

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 March 31 as the common date.

Date: March 31

GDD Unit Accumulation

2024

110

2023

52

2022

83

2021

95

2020

46

2019

28

2018

47

2017

115

2016

114

2015

10

2014

9

2013

32

2012

237

2011

23

2010

56

2009

82

2008

36

2007

86

2006

50

2005

35

2004

57

20 Year GDD Average for Toledo (43615) on March 31 - 65 GDD Units

More Information

The Ohio State Phenology Calendar Website

https://weather.cfaes.osu.edu/gdd/