Jack Pines on Lake Michigan's Southern Shore

Jack pine trees (Pinus banksiana) are often found growing near coastal intradunal wetlands known as "pannes."

NPS / Zachary Lindeman

The jack pine tree (Pinus banksiana) is a unique species at Indiana Dunes. Typical of evergreen forests of the north, this species finds its southernmost natural populations along our shores. They can be identified by their gray bark and short needles that grow bunches of two in a "V" formation. Oftentimes they are found with other boreal species like arctic bearberry (Arctostaphylos uva-ursi) and common juniper (Juniperus communis). Unlike the tall white pines (Pinus strobus) found on our dunes, jack pines here are shorter and scrubbier, usually not exceeding a couple dozen feet. In their optimal growing conditions further north, jack pines can reach 70 feet. How did they get this far south?

In 1925, Dr. Henry Chandler Cowles and Bertha Morris Parker from University of Chicago's School of Education published The Book of Plants for middle school-aged students. In the book, Cowles includes a chapter on jack pines trees to shed light onto why this species can be found at Indiana Dunes. Read the excerpt below:

The Story of the Jack Pines

By Dr. Henry Chandler Cowles

Range map of the jack pine tree (Pinus banksiana) in green.

USGS

If you have ever been in the dune region at the southern end of Lake Michigan, you have probably seen Jack pines like those in the picture [above]. If you have seen them, it doubtless didn’t occur to you to wonder how they happen to be there. A glance at the map . . . will show you, however, that it is really very puzzling to find them there for they are much farther south than Jack pines can be found in any other place in North America. And the Jack pine grows only in North America. Jack pines are trees of the Far North. They grow with the spruces and firs in the great evergreen forests which stretch across the continent. How, the, does this “island” of Jack pines happen to be so far south of where the Jack pines really belong? The answer to this plant puzzle is a long story.

Historic photograph by Ira Benton Meyers of a jack pine (Pinus banksiana) forest growing along the lakefront near Gary, Indiana in 1903.

University of Chicago Photographic Archive, aep-inn179, Hanna Holborn Gray Special Collections Research Center, University of Chicago Library.

A few [thousand] years ago the Jack pines grew in the evergreen forests of the north just as they do to-day. Probably none of them grew so far south as the region which is now northern Indiana. In the region where the pines grew, the winters were long and the summers were short, as they are now in the evergreen forests of the north. The Jack pines could have spread to the south had there been any room for them, but there were so many oaks and maples and other hardwood trees to the south that there was no room for these pines.

Illustration of jack pine (Pinus banksiana) needles by local naturalist William D. Richardson, husband of naturalist and conservationist Flora Richardson.

Westchester Township History Museum

Gradually in the north where the Jack pines lived it grew colder. The winters became longer and the summers shorter and shorter. The summers became so short that not all the snow that fell in the winter melted the following summer. Each winter more snow was added to what was left at the end of the summer before. After many, many years the snow on the ground had become very deep. Little by little this great mass of snow became a mass of ice—a glacier.

It kept on snowing and the ice grew thicker. It snowed more and the ice became still thicker. Can you imagine a sheet of ice many times thicker than your school building is tall, and covering hundreds of square miles? If so, you have some idea of the size of the glacier.

Jack pine trees (Pinus banksiana) along Lake Michigan's shore at Indiana Dunes.

Joe Gruzalski

Very gradually the ice spread southward. As the ice came toward the Jack pines, the climate became so cold that they could not live there any longer. Many of the animals that lived in the forests with the Jack pines went farther south to live. A plant, of course, cannot do that. There is one part of a pine which can travel, however. That is the seed. As the ice approached, some of the seeds of the cones fell near by and stayed there, but some were carried away, perhaps by the wind, perhaps by animals. The ones which were carried toward the ice did not grow. Those which fell near the trees which bore them started to grow, but many of them were killed by the cold. Many of those that were carried to the south grew. How could they grow when the hardwood forests were in the way? There was room for them now where the oaks and their neighbors had been, for the northernmost of these trees had been killed by the cold.

Early 1900s photograph from Indiana Dunes of the tip of a jack pine (Pinus banksiana) branch with a pinecone by William Johnston Cribbs.

University of Chicago Photographic Archive, aep-ins255, Hanna Holborn Gray Special Collections Research Center, University of Chicago Library.

The ice kept on spreading, Only from the seeds that were carried farther and farther south could the pines grow. And there was always room for them, because the hardwood forests were being pushed to the south, too. It was like a great march to the south with the Jack pines taking one step each year. Of course, the spruces and firs and other neighbors of the Jack pines traveled with them.

Had the ice spread rapidly from the north, all the pines would have been killed and buried under it. But the ice spread so slowly that the pines and their neighbors managed to keep ahead of it.

Modern-day photograph from Indiana Dunes of the tip of a jack pine (Pinus banksiana) branch with a pinecone.

NPS / Zachary Lindeman

So it went on for thousands of years. At last all of what is now Canada was covered by this great ice sheet. Still the ice kept spreading. Almost all of what is now Wisconsin and Michigan and Iowa and northern Illinois was finally under this great sheet of ice hundreds of feet thick. Jack pines could grow then only from seeds that had been carried as far south as southern Indiana and Illinois, and the hardwood forests were farther south than this.

After a great many years it began to grow warmer. The ice at the southern edge melted. Hardwoods could then grow in the same region where the Jack pines and their neighbors were, and the Jack pines and firs and spruces were crowded out. Only from the seeds that were carried north toward the ice could these trees then grow. As the ice continued to melt, the Jack pines and spruces and firs . . . were pushed to the north by the hardwoods. And so it went on. Four times at least the hardwood forest pushed these evergreens north.

Jack pine tree (Pinus banksiana) in a coastal dune complex near Lake Michigan.

NPS / Zachary Lindeman

As the hardwood trees, for the last time, pushed the Jack pines to the northern part of what is now Indiana, some pine seeds fell in barren sandy soil near what is now the southern end of Lake Michigan. Trees grew from these seeds. These Jack pines were probably not so large and strong as those growing with the firs and spruces on the richer soil near by, but many of them were able to live.

Hundreds of years went by. The spruces and firs and Jack pines were crowded out from the good soil roundabout the hardwood forests advancing from the south. But the hardwood forests could not crowd out the Jack pines from the more barren soil near the southern end of the lake, because the hardwood trees themselves could not grow there.

As time went on dunes were formed in this sandy region. Jack pines grew on the young dunes.

Lush jack pine trees (Pinus banksiana) within a coastal dune complex at Indiana Dunes.

NPS / Zachary Lindeman

Farther and farther north the evergreen forest was pushed, but still the Jack pines remained in the sand dune region near the lake. And there they are today—relics of the great ice age. True, even now, as soon as a sand dune becomes a fit place for oaks and their neighbors, the Jack pines are crowded out. But there always are new dunes which are not yet fit places for oaks, and on these the Jack pines grow. Whenever you seen them, they should remind you of the time when a large part of North America was a barren dreary waste of ice and snow.

---

Jack Pines at Indiana Dunes Today

Jack pine trees are relics of the Ice Age, reminders of a time when an enormous sheet of ice covered northwest Indiana. They are a state-listed species that are able to survive in poor soils and harsh conditions where other species cannot grow. In terms of plant succession; they are often found near the lakeshore, typically after cottonwood trees but before oaks. Their presence at the park along with other boreal species of the north is a testament to the region's diverse habitats and its role as a refuge for various species.

Look for jack pines along the Dunes Succession Trail at West Beach or along the Paul H. Douglas Trail in Miller Woods. Please help us protect these habitats for the benefit of this and future generations by only exploring on officially-designated trails.