This is your mid-day almost-spring wakeup call from OSU’s Secrest Arboretum in Wooster. It will be the earliest vernal equinox in 124 years tonight at 11:49 in our time zone. “Equinox” comes from the Latin equinoxium, for the “almost” equal amount of day and night. Two more earliest years are coming in the leap years of 2024 and 2028. So, is it an early spring, phenology-wise?
Phenology is the matching of biological and environmental events, such as plant flowering and insect activity. That match is a useful metric because organisms respond to the buildup of growing degree days (GDD) for a given growing season. In Wooster and Secrest Arboretum, in northeast Ohio, the growing degree days are pretty normal for the last few years. As of this morning, they are at 43, in 2019 they were 57, and in 2018 they were 36. It was certainly a mild winter, but not too many days exceeded 50.
You can calculate the increase of GDD (they never go down no matter how cold it is) by taking the high temperature for the day over 50 divided by 2, so our predicted high in Wooster today of 61 will increase GDD by 5.5 to 48.5 (61-50/2) today and of 67 tomorrow by 8.5 to 57 (67-50/2). What does this mean for plants? Corneliancherry dogwood (Cornus mas = there’s that Latin again!) has its first bloom (1 of 20 flowers are out) at 40, so it has started to bloom in Wooster already, silver maple (Acer saccharinum) is at full bloom (19 of 20 blooms are out) at 42, and red maple (Acer rubrum) has its first bloom at 44, so it shall happen in Wooster today. Coming up ‘Northern Lights’ forsythia = 58; border forsythia = 86.
Cool stuff. Where can you get a phenological calendar? We are fortunate in Ohio as we have a great resource for all Ohio zip codes, thanks to the Ohio State Phenology Calendar developed at OSU by Dan Herms, Denise Ellsworth, and John Cardina with the website programming, development, and weather station integration by Dave Lohnes (https://www.oardc.ohio-state.edu/gdd/). Keep up to date on what is here and yet to come – depending on the weather.
So, what is happening at the great socially-distant outdoors of Secrest Arboretum?
Well, those corneliancherry dogwoods are glorious and a touch less intensely yellow-orange as the dandelions, out for some time. Witchhazels (Hamamelis): our native Hamamelis vernalis and the many cultivars of the Chinese and Japanese hybrids (Hamamelis xintermedia), are soon to start fading from their earlier winter blooming, and spring beauty wildflowers are at now showing their foliar prelude to their delightful blooms.
Of course things will soon move forward with our two degree-day accumulating days in the 60s today and tomorrow, followed by a potentially plant-damaging plunge in Wooster tomorrow; high of 68 low of 28, then colder yet with a low of 23 on Saturday, followed by degree-day buildups again next week. And, of course, all of this differs for your zip code reality further south and further north in Ohio.
There are also some stark reminders of winter with their own sort of beauty. Check out the remnant bagworms not singing in the dead of winter; they are only waiting for their moment to arrive (GDD= 630 for initial bagworm egg hatch) adorning trees. See how baldcypress and dawnredwood look now before spring green-up in April and May, look at the ominous aspect of hardy orange (Poncirus trifoliata).
And note that OARDC’S grounds manager Roger Hamilton and his colleagues continue their winter and soon spring work, including needed pruning of Taxus (with beautiful wood) and other plants. Finally, the Pieris japonicum (GDD = 60) is ready to pop!