What will the recent warm temperatures do for our plants?
Weather is always on our mind this time of the year. Tornadoes and strong winds went through some of Southwest Ohio recently, wreaking havoc on homes and trees. Fortunately, no one was injured, but there were a lot of trees down.
The other part of weather that concerns us (much less than the above-mentioned situation) I mentioned last week in terms of cold temperatures and the potential for plant damage. The big question is what will the recent warm temperatures do for our plants?
The answer is to wait and see. Spring temperatures and plant damage all depend on the stage of plant development at the time temperatures drop, how far they drop and how warm it was before they drop.
People are also assuming that we are much further ahead in terms of plant development this year compared to last. Let’s take a closer look.
I use growing degree days (GGD) to compare plant development from year to year. GDDs are a measurement used to look at the growth and development of plants and insects during the growing season.
GDDs are based on a specific formula, using 50F as the base temperature. The high and low temperature for a day is averaged, and 50F is subtracted from the average. If the average is 55, for instance, we gained 5 GDD.
GDDs don’t go backward; plant development in the spring doesn’t go backward! If subtracting 50 results in a number below 50, GDDs stay the same. It’s only if the resulting number is above 50; GDDs only move forward.
We gain more GDDs when night temperatures are warmer than normal night temperatures. If night temps stay in the 50s and day temps are in the 70s, you easily gain 10 to 15 GDD in one day.
Looking at the website weather.cfaes.osu.edu/gdd, you will be able to see where we are at any given point of time for GDD. For instance, using my zip code, my landscape is at 63 GDD on March 5. On the same day last year, we were at 83 GDD, ahead of this year.
On the same date in 2022 and 2021, we were 31 GDD and 10 GDD, respectively. When people comment that we are way ahead of last year in terms of spring flowering, I refer to the GDD page to see if that’s true.
GDDs are also used to help predict insect emergence. For instance, the white pine weevil adult emerges at 84 GDD and the first bloom of the star magnolia appears at the same time.
Therefore, if you are planning on controlling the white pine weevil, you can monitor its emergence by watching the star magnolia. It’s an easy way to monitor insect emergence.
So, while we may be ahead of 2021, we are behind last year’s spring blooming pattern.
I encourage you to explore the website and use your zip code to determine where we are in terms of GDD. It’s a great site, with information based on years and years of research and evaluation.