Gardening Rocks

20,000 years ago, New England
was under a mile-thick sheet of ice

Twenty thousand years ago, New England lay under a mile-thick layer of ice.  Glaciers pushed down from the north, sculpting the land as they pushed southward as far as what is now southern Illinois.  Then, some ten thousand years ago, those glaciers gradually retreated, leaving behind terminal moraines that became Long Island and Cape Cod, and creating the Connecticut and Hudson River valleys.  Playing sand castles on some cosmic scale, glaciers gouged out the Great Lakes and New York’s Finger Lakes.

Louis Agassiz

The glaciers also occasionally ‘burped’, leaving piles of rocks in odd places.  Areas of bedrock proved to be the immovable objects against which the otherwise irresistible force of the glacier was forced to go over rather than through.  As the glacier moved, it pushed along sometimes enormous chunks of rock it had gathered from more pliable formations. 

Until the nineteenth century, the above paragraphs would have been considered something between nonsense and heresy, especially in the United States. Everyone ‘knew’ that Noah’s Flood had been responsible for the shape of lakes, rivers, and mountains.  Then, in 1837, Swiss Professor Louis Agassiz proposed the theory of glaciation.  His work caught the attention of Boston philanthropist John Amory Lowell, who induced him to emigrate to America, where the ‘Noah’s Flood’ theory was still firmly entrenched.

In the background is 'Little' Agassiz.  Double-click to see
the family at its base.

Agassiz settled at Harvard and found the New England coastal plain to be a proving ground for his theory.  Over several decades, glaciation came to be the only rational explanation for ‘errata’ like giant rocks atop hills that were hundreds of miles from their point of origin.  One of the prime examples of such ‘errata’ was a pair of rocks in Manchester-by-the-Sea, Massachusetts.  In 1874, at the end of his career, Agassiz visited the site and confirmed what his students had found: a glacier had pushed up and left behind these rocks.  The site was named for him.

On Saturday, Betty and I hiked half a mile from the nearest road to observe these rocks, which more than lived up to advance billing.  We were at the top of a prominent hill overlooking the countryside and there, in two locations, were these barn-sized rocks, the smaller of which was resting at an improbable angle.

A Google Maps view.  The white area marks the site
surrounding 'Little' Agassiz.

We were able to do this because, decades ago, someone gave a large chunk of land (which was later augmented by additional gifts) to an organization called Trustees of Reservations.  In Massachusetts, the Trustees own vast swaths of ecologically sensitive or historic land.  Their goal, stated elegantly, is to protect the region's heritage for future generations. 

The Agassiz Rocks Reservation is a rounding error in the Trustees holdings, a few hundred acres in a part of Massachusetts that has dozens of similar sites (including the Trustees’ ‘crown jewel’, Crane Beach).  While there are marked trails and an evident effort to ensure that ordinary walkers can get from the road to the rocks (and beyond), there’s no admissions gate or other barrier to entry.  On an early October day at noon, there was just one other car in the parking area.

Clethra grows wild, too

I write all this because, when the gardening season draws to a close, it is time for gardeners to go exploring new places and see what nature can teach them.  Saturday offered a few eye-opening lessons.  The first was seeing a grove of clethra surrounding ‘Big Agassiz’.  To me, clethra is a ‘suburban’ shrub; we have half a dozen compact specimens in our garden.  But there it was: an expanse of clethra growing as nature intended in a boggy area at the base of the rock.  It was, in its own way, an epiphany.

The ferns at the top of a rock

Then, there were the ferns.  Betty saw them first: they were improbably ensconced fifteen feet up at the top of an enormous rock.  The ferns were thriving where they ought to be washed away with every rainfall and erased out of existence with each winter.  Were they growing in a quarter inch of leaf litter, or had their roots found purchase in unseen crevices?

With luck, yesterday started a new season of discovery and of learning.