A common stereotype that surrounds the concept of a “mountain” involves either a summit populated with coniferous (evergreen) trees, or a treeless summit surrounded by coniferous forests below the treeline. Indeed this assumption holds mostly true for many mountains in New England, including the famous Mt. Washington, Mt. Cardigan, Mt. Monadnock, and Pack Monadnock. A strange phenomenon exists on the nearby Mt. Wachusett, however. Instead of a summit of conifers, Red Oak dominates the available soil.

Why might this be the case? Despite being only about 30 miles south of Pack Monadnock, and only 200 feet lower in elevation, the ecological communities of Mt. Wachusett’s summit differ drastically in character. Pack Monadnock showcases a beautiful array of spruce mixed with northern hardwood species mosaics (beeches, birches, and maples) on and around its summit. The very top of Mt. Wachusett, on the other hand, is a scrubby patch of red oaks surrounding the bare summit. It’s beautiful and fascinating in its own way, but a bit confusing.

That’s not to say Mt. Wachusett is completely devoid of northern hardwoods or spruce. In the ideal growing conditions on the northern slopes, many of these species tend to dominate, particularly the yellow birch. However, old growth oak is still a mainstay throughout these forests. Red spruce is limited to a narrow band on the northern slope just below the summit, but does not breech the ring of scrub oaks at the top.

There could be a few reasons for this interesting phenomenon. While much of the research on Mt. Wachusett’s ecology has involved documenting its old growth forest below the summit, there are a few historical and environmental clues that we can use to try and explain the oaks without doing scientific research ourselves! The further south we go in New England, generally the more frequent fire regimes become. While cold ravines and slopes are protected from fires for long periods of time due to their moisture retention, the exposed summit of Wachusett may not retain as much water, allowing fire regimes to historically reign more frequently in this area. Oaks are a species that tend to thrive in areas that are a little drier, and see a little bit more fire, than red spruce and northern hardwoods. In fact, red spruce is particularly susceptible to fire damage.

Another possible explanation is the more recent active disturbances on the summit, which included various recreational structures over the last century. Trees were at different points cleared out to make way for roads and buildings, but the areas of disturbance have evolved over time, potentially allowing some forest to grow back. Red oak is considered to be an early to mid successional species, while red spruce is a late successional species. While climate change may drive the spruce out of this area entirely at some point, without that factor we could have seen more spruce begin to grow in the shadow of these oaks over time, perhaps replacing some of them in the canopy eventually. These are just theories of my own imagination, though, so perhaps scientists will seek to definitively explore this question at some point.

Mt. Wachusett poses this question to us laymen, but it has been studied for almost two decades now thanks to the discovery of four distinct areas of old growth on different slopes of the mountain. This was a particularly incredible find for the area because there were virtually no known old growth areas east of the Connecticut Valley in Massachusetts of this forest type. Many of the other known old growth areas lie in swampy or sandy unfarmable land down towards Cape Cod and Plymouth, and these forests have a much different ecological composition than areas further from the shore.

Wachusett’s old growth areas showcase distinct characteristics depending on their location on the mountain. On the Old Indian Trail, which lies on a north facing slope, we tend to see a transitional hardwood forest, consisting of the aforementioned yellow birches of varying size and age, as well as extremely mature red oak trees, some of which have exceeded their expected lifespan. The harshness of the terrain and frequency of wind events have actually protected these strong old trees that have stood the test of time, knocking out weaker competitors and leaving an open canopy for them to flourish.

There are four total distinctly studied old growth areas of the mountain. I have not yet visited all of them in person, but in three we can find similar mixed stands of yellow birch, American beech, red oak, and red maple, though the predominance of each type varies. On the southwestern portion of the mountain, we can also find a stand dominated by old growth hemlock.

For easy access to the most well known old growth area of the park, you will need to pay a $5 fee to enter the road that leads to the parking lot across from the Old Indian Trail. You can also start hiking from the base of the mountain closer to the ski resort village. When I went in the summer, the environment was fairly hot and humid with a decent number of mosquitoes, so bug spray is recommended during peak summer. Winter hikes may require microspikes and/or snowshoes depending on recent snowfall amounts. Like most hikes in Massachusetts, spring and fall are the best times for avoiding the most extreme of conditions.