“Plant beans and squash when the lilacs are in full bloom,” or “plant peas when you hear the Spring peepers” are based on animal and plant behavior related to the accumulated warmth of the season. In the era when everyone farmed, at least on a subsistence level, such observations were once commonplace and widely used, as they could mean the difference between feast and famine.
As folksy as it sounds, there’s a fancy name for these observations: phenology. “Most of these happenings are temperature-dependent, not calendar-dependent. The opening of some buds and the emergence of some insects from the ground are related to the “growing-degree days,” a calculation based on the average high and low temps over time. It isn’t just superstition that some events occur simultaneously every year, but on dates that change from year to year. It is the result of two events being triggered by the accumulating warmth having reached a certain threshold.” (excerpted from a Nov-Dec 2016 article by Pam Dawling in the Growing for Market magazine).
Phenology can also mean tracking a single plant or animal behavior over time to see how it changes from year to year. People—most notably, Thomas Jefferson, Aldo Leopold, and Henry David Thoreau—have tracked bloom time, insect emergence, and other natural occurrences for centuries. As our climate changes, data from citizen scientists and researchers across the country is creating a record of long-term trends in these plant and animal behaviors. The National Phenology Network and Project Budburst are two clearinghouses for this data, which can be used to support habitat conservation, climate-informed monitoring, and adaptive management of ecosystems.
And don’t forget farms and gardens! Understanding phenological signs for your area can help you get your plants in the ground at the right time, and can also help predict pest emergence. Apparently the first flea beetles emerge when the redbuds are in bloom, so when you see those trees blossoming, cover up your broccoli and eggplant!
I love the idea that phenology requires no fancy training or expensive tools but simply a sense of curiosity, a sharp eye, and a notebook. If we pay attention, we can observe patterns over time that will make us better land managers and naturalists.
I hope you planted your sweet corn when the white oak leaves were the size of a squirrel’s ear (really?)! What phenological observations have you made? Did you grow up hearing any from a farming or gardening relative? I’d love to hear them! Please share in the comments section below.