Pages of pressed plant specimens from Thoreau's Herbarium in the collection of the Harvard University Herbaria.

Changing climate and flowering times in Thoreau's woods

Among the many observations made by author and naturalist Henry David Thoreau were his careful notations of seasonal changes, including bird migrations, the emergence of tree leaves, and the appearance of buds and flowers in the spring. How have these phenological events been affected by recent climate change?  In this activity you will gather and analyse data recorded by Thoreau and other naturalists and scientists that show the change in one phenological event–the time of first flowering–as observed over 160 years.

Teachers Guide

The comprehensive Teachers Guide includes a detailed lesson plan, background information, key vocabulary, and additional resources.

Video Resources

Welcome to the Harvard Herbaria

In this introduction to the Harvard Herbaria collections, Charles Davis, Professor of Organismic and Evolutionary Biology and Curator of Vascular Plants, describes the history of the Harvard plant collections and the different ways they have been built and used from their origins to today. (6 min.)

Using Herbarium Data to Better Understand Climate Change

Charles Davis shows how digitized collections at Harvard and other herbaria provide clues to how climate change has affected flowering times in the wooded areas of Concord, Massachusetts and other locations world-wide. (7 min.)