Is it Jack Frost or Jack Pine?

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The holiday season is here, bringing with it the joy of decorating Christmas trees, baking cookies, singing carols, and more. A prominent symbol of this season is the pine tree which can be seen everywhere. From famous holiday displays at Chicago’s Millennium Park or New York City’s Rockefeller Center to homes across the country. Pine trees, part of the Pinus genus with about 115 species, are found worldwide though they’re primarily native to northern temperate regions. These trees are valuable for both the environment and for people, offering food and shelter to wildlife, erosion control, and improved air quality. 

The Indiana Dunes National Park is home to a unique species called the jack pine (Pinus banksiana). The jackpine can be identified by its fascicles (groups) of two short dark green needles and its gray, flaky bark. It grows between 35 and 65 feet tall and prefers acidic, well-drained sandy soil. Currently the evergreen tree is native to the southernmost regions of Wisconsin, Michigan, and Minnesota, extending northward into Canada. Given that its optimal growing conditions are much further north, how did jack pine trees find habitat in the Indiana Dunes? 

Dr. Henry Chandler Cowles, a renowned botanist from the University of Chicago, explored this question in his work The Book of Plants. Around 11,000 years ago, hardwood forests of oak and maple trees were abundant in the southernmost regions (Wisconsin, Michigan, and Minnesota) creating an environment too crowded for jack pines. As the climate shifted, winters grew longer and summers shortened. One might imagine that jack frost gifted a vast accumulation of snow that over time turned into ice, known as the Ice Age. Under the pressure of its own weight, a glacier will begin to move outwards and downwards. Glaciers periodically retreat or advance depending on the amount of snow accumulation or melt. The jack pines could not survive the rivers of ice and their seeds spread further south to Indiana and Illinois.

The pine seeds remained in the barren sandy soil of the young dunes as the glacier slowly melted and retreated north. Hardwood forests could no longer thrive in the conditions of the sandy terrain as the temperatures rose, allowing the jack pines to thrive. These trees, now considered relics of the Ice Age, have proven resilient enough to withstand poor soil and harsh conditions. At the Indiana Dunes, you can find jack pines along the lakeshore on the Dunes Succession Trail at West Beach and on the Paul H. Douglas Trail in Miller Woods. 

Ixchel Barraza Zapata

Environmental Education Fellow