Where Are Henry David Thoreau’s Plants Now?

[Thoreau’s] journals offer an unparalleled phenological record — that is, a log of the timing of events, like a first flower or leaf growth. Looking back through Thoreau’s logs, as well as those of later botanists, Primack and Miller-Rushing found the first flowering date for 43 of the most common species has moved up by an average of 10 days.