August 30, 2026: Jack Pine

On a recent hike to Mt. Chocorua I passed through a rare natural habit, so rare in fact that it's recognized by the N.H. Natural Heritage Bureau as a critically imperiled (S1) natural community due to its small population and limited habitat.  It's the Jack Pine Rocky Ridge Natural Community, dominated by the Jack Pine tree (Pinus banksiana).  

Jack pines set root in soil held in small crevices in rock scraped bare by glaciers

In New Hampshire the jack pine is a remnant from the colder climate of the last ice age.  Because it can tolerate cold temperatures and harsh growing conditions, it was a dominant species as the glaciers melted.  As conditions improved over time, warmer climate species were able to take hold and crowd out the jack pine in most of New Hampshire and the Northeast. 

Short, sturdy needles retain moisture through dry, cold, windy winters.

Farther north in Canada's boreal forests where the climate is harsher and the growing season shorter, less hearty trees can't thrive, and jack pine continues to be a prevalent species.  But on the high elevation, wind-swept ledges of the Chocorua Range, jack pine is one of the few plants that can eke out a living in the thin acidic soils left after the ground was scraped bare by the glaciers. 

The barren landscape of Carter's Ledge on Mt, Chocorua.

Here, where less hardy trees can't compete, this rugged, boreal conifer is at the far southern edge of its present range.  The bent and twisted form of the jack pine on the Chocorua Range is testament to the harsh conditions and strong winds that can occur in the White Mountains even on mid-summer days.  

Jack pines typically have serotinous cones than remain unopened on trees for years until a forest fires with temperatures over 120 F releases their seeds. 

But jack pines in New Hampshire generally have semi- or non-serotinous cones that can release seeds on just a very hot summer day which keeps our small populations in place without fires.  However, according to Tom Wessels, the community on Chocorua has many more serotinous cones than the other New Hampshire communities.  [The Granite Landscape, Tom Wessels, 2001, Countryman Press, pg 99]  Wessels attributes this difference to the pines on Chocorua having migrated uphill from lower elevations that had frequent forest fires after the glaciers retreated.

An open jack pine cone with seeds dispersed.

Somehow, on these harsh, open ledges, jack pine continue to defy the elements, with each tree growing in the most precarious location, hanging on until eventually a strong enough wind brings its demise.

A Jack Pine clinging to the rim of Carter Ledge.

You can explore this rare community (there are only three known communities in the state) by following the Piper, Nickerson Ledge, and Carter Ledge Trails up to Carter Ledge.  You'll know it when you get there.  

Mt. Chocorua (left) and Middle Sister (right) seen from Carter Ledge.

More information on the jack pine and the jack pine natural community can be found in the book The Nature of New Hampshire by Sperduto and Kimball, or online in the Manual of Natural Communities of New Hampshire.

There's another interesting natural curiosity that anyone who's climbed Mt. Chocorua has probably noticed - this dramatic basalt dike that the Liberty trail crosses near the summit.

I'm not well versed in geology, so here's an edited version of what AI provided as a description of this particular formation.  AI referenced The Geology of the Percy Quadrangle by Chapman, and Geochemistry of mafic dikes in the Adirondack mountains by Coish and Sinton.

Hundreds of millions of years ago,  intense tectonic pressure deep underground cracked open the lighter-colored granite bedrock of the White Mountains.  Dark, molten basaltic magma was forced upward into these vertical fractures (this is called magmatic injection) and cooled relatively quickly to form narrow vertical sheets of rock known as dikes. 

As this ribbon of magma cooled between the granite walls, it shrunk and fractured at regular intervals, creating a pattern of horizontal fractures called columnar or sheet jointing.  These perpendicular breaks segmented the rock into blocky layers.  

After the glaciers stripped away the surface soil and exposed the peak, New Hampshire's weather and freeze-thaw cycles took over.  The dark basaltic rock is softer and more susceptible to chemical and physical weathering than the surrounding granite, so the dike eroded faster.  Rain and melting snow seeped into the dike's fractures, froze, expanded, and popped out blocks of the dark rock leaving the step-like features.

 Here's a close up view of the eroding dike.

The Liberty Trail crosses this fracture several times.  Just east of the summit on the Piper Trail is an area of basalt cracking where the rock is course grained and breaking away.

We spent this week north of the notches in Lancaster near the Pilot Range, which has its own interesting geology; I need to read more about that mountain range formation.  And right here at Lake Wicwas there's plenty of interesting geology to be found in the ledges and talus fields of Crockett's Ledge - maybe I'll dive into that someday.  Anyway, I didn't spend time on the lake this week, so yesterday I poked around a bit to see what's blooming here in late August.  I found the usual late summer flowers, and a couple of new ones including a foxglove and a meadow-rue.

Purple False Foxglove

A meadow-rue, perhaps King of the Meadow 

Self-heal

Yellow Wood Sorrell

Turtlehead, a fall favorite of mine.

I'll close with a sign of the waning summer:  Cat-o-nine tails starting to shed their seed cones.

There's an even more ominous sign hiding in the background, which becomes more evident with a change in focus.

Yes, leaves are starting to turn.