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Home > Publications > Historic New England Magazine > Fall 2003 > Telling Time by Tree Rings

Telling Time by Tree Rings

ABOVE Half-inch core sample from the United Methodist Church, Townsend, Massachusetts, showing 128 growth rings.

"SPNEA has made a recent break-through of major proportions in its efforts to mount a dendrochronology study, enabling for the first time in New England history the precise dating of oak timbers in early buildings through scientific analysis."

-Abbott Lowell Cummings

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The lack of documentary evidence surviving from the early colonial years has made it difficult to date New England's earliest buildings. Dendrochronology, a method of dating historic timbers and wooden artifacts by analyzing tree ring patterns, has been available elsewhere since 1926 but has not been used in New England because the fundamental groundwork of identifying the region's tree-ring patterns had never been done. Now, building upon earlier work by former SPNEA Director Abbott Lowell Cummings, SPNEA has undertaken a dendrochronological project that has made it possible to pinpoint the construction dates of many First-Period buildings.

The science of dendrochronology relies on climate-related variations in ring widths-trees grow more in wet seasons than in dry ones. The resulting thick and thin growth patterns are similar in trees of the same species grown in the same region. To establish a chronology, scientists take core samples first from standing trees and then from buildings of increasingly older dates. By matching patterns in the samples, they can develop an uninterrupted sequence of tree-rings reaching back from the present to well before the construction dates of the oldest buildings. Undated samples can then be compared to the master chronology and dated.

SPNEA's dendrochronology project, led by former staff member Anne A. Grady, was supported by grants from the Massachusetts Historical Commission and an anonymous donor. Since the project began in 2000, consultant dendrochonologists Dr. Edward Cook and Paul Krusic of the Lamont-Doherty Earth Observatory of Columbia University, and Daniel Miles and Michael Worthington of the Oxford Dendrochronology Laboratory in Oxfordshire, England, have taken core samples from timbers in thirty-one buildings and several stands of old-growth trees. They have successfully developed master chronologies for red and white oak, which are now being used to date buildings in eastern Massachusetts, southern New Hampshire, and Rhode Island. The fact that the first settlers generally built with green timbers allows us to pinpoint construction dates within a year of when the trees were felled. Eight of SPNEA's oldest buildings were studied; the results have in several cases significantly revised our understanding of their history.

-Anne A. Grady,
Preservation Consultant

Telling Time by Tree Rings