Phenology: Climate and Seasonal Biological Events

July 13, 2017

By Paula Goodwin

Phenology: Climate and the Timing of Seasonal Biological Events

In early spring it is cheering to see the appearance of Snowdrops, crocuses and spring ephemerals that bloom before the trees have leafed out. After the growing season, in the fall, we notice the leaves change color to orange, yellow, red and gold as the leaves’ green chlorophyll fades away.

Phenology is the word used to define the study of how the biological world times natural events. Plants and animals take their cues from their local climate. Climate (long-term weather patterns) is impacted by three non- biological factors that work together: temperature, precipitation and available sunlight. Species use the predictable yearly changes in the climate to determine when they start natural events such as breeding or flowering. These changes in nature inspire many people to keep nature journals.

Clare Walker Leslie, author of the book, Keeping a Nature Journal explains, “whereas a diary or personal journal records your feelings toward yourself and others, a nature journal primarily records your responses to and reflections about the world of nature around you.” This past April, observations of a tree inspired an Acton resident to record: “April 19, 2017 – I don’t remember identifying this tree before. It’s in flower, on the neighborhood side of my house, at the edge of the little woods. Sweet cherry (Prunus avium). I learned that the sweet cherry is an introduced species, but not invasive. It flowers quite early, before the leaves are fully out. If we get fruit, it’s edible (and good in pies) when fully ripe. I don’t remember if this one gives fruit. I also learned that although it’s very similar to sour cherry, the way to distinguish it is that sour cherry has less than 8 parallel veins on it’s leaves, and sweet cherry has more than 8.”

From 1837 to 1861 Henry Thoreau recorded the dates of plant changes he observed after walking in Concord for several hours every day. He took notes on the phenology of different species of grasses, wildflowers, shrubs, and trees he encountered. The charts he created are significant phenology resources.

UMass Extension’s Landscape Message is an educational newsletter intended to inform and guide Massachusetts Green Industry professionals. It also is of interest to the home gardener for its phenology reporting of bloom times and garden pest updates.

Metro West data is collected in Acton. See the resource list below for the website address. You can subscribe to receive the Landscape Message by email.

The USA National Phenology Network encourages people of all ages and backgrounds to observe and record phenology as a way to “discover and explore the nature and pace of our dynamic world.” The Network makes phenology data, models, and related information freely available to empower scientists, resource managers, and the public in decision-making and adapting to variable and changing climates and environments. Their Nature’s Notebook program is a citizen science opportunity! You can participate by going outside to observe nature in your backyard or nearby area weekly and enter the information online.


Concord Museum-Henry Thoreau and Phenology: exhibition.php?page=3

National Wildlife Federation:

USA National Phenology Network:

Nature’s Notebook:

Umass Extension Landscape Message: