My family and I live in the leafy West Mount Airy neighborhood of northwest Philadelphia, largely developed between the arrival of Victorian commuter lines and World War II, but with a smattering of houses showing its early nineteenth century rural beginnings. When I walk down my front steps, by turning left or right I can quickly move from one local watershed to another: the Monoshone Creek and Carpenter’s Run. Each of these merges with the Wissahickon Creek, famous locally for its eponymously named schist, and each watershed provides clues into the arboreal history of northwest Philadelphia.
Our neighborhood is known for its high percentage of canopy cover, and at first glance, it may not seem much different than other semi-urban neighborhoods, with much of this cover intentionally planted over the past 100 years. But what distinguishes the neighborhood are the naturally occurring remnant forests that in some cases are obvious, and in others a less transparent component of the urban canopy. The diversity of houses also distinguishes the neighborhood, and includes large single houses with ample yards, a mix of semi-detached houses of varying styles (some with space around them and others crowded together), and tightly packed row houses. In addition to this diversity in style and density, there is a wide range of age diversity, with occasionally eighteenth and nineteenth century vernacular farmhouses, early Queen Anne and Italianate “commuter” houses from the late 1800s, a large mix of pre-World War II houses of varying styles, and even some more contemporary additions.
When turning right from our front steps, and heading to the crest of our block, I quickly enter Carpenter’s Woods, a watershed separate from the one in which we live. The story told by Carpenter’s Woods—with its canopy of mature Eastern hardwoods contiguous with the larger Wissahickon Valley Park—is perhaps more obvious than that of the rest of the neighborhood. Likely forested in the eighteenth century, these woods were preserved in the early twentieth century when they became part of the Philadelphia Parks system because of their importance to a diversity of resident and migratory bird species; today, they remain part of a network of places recognized for its value to bird conservation. The preservation of Carpenter’s Woods also reflects a difference in land ownership since the 1700s, it being comprised of a few large parcels in comparison to smaller individual landholdings in adjacent areas.
Carpenter’s Run courses through these woods as a free-flowing stream for almost its entire length. This run, a headwater whose drainage boundaries are well defined by the intact canopy of Carpenter’s Woods, gives the woods a distinctive panhandle shape reminiscent of Oklahoma. It is fairly clear that the woods and its watershed are closely the same, and so it is fairly obvious to understand the drainage area of this watershed. Here you will find a mix of eastern hardwoods: large tulip trees (Liriodendron tulipifera), white oak, chestnut oak, and black and red oaks (Quercus alba, Q. velutina, Q. rubra, and Q. montana), an occasional hickory (Carya cordiformis), American beech (Fagus grandifolia), sassafras along its edges (Sassafras albidum), black cherry (Prunus serotina), Eastern white pine (Pinus strobus), red maple (Acer rubrum), black birch (Betula lenta), sycamore (Platanus occidentalis), blackgum (Nyssa sylvatica), and white ash (Fraxinus americana). Some of these are massive and demonstrate their ages, while others (in particular the white oaks) have sizes that belie their age. Core samples of white oaks, blackgum, and tulip trees all show these to be over 200 years old, providing real evidence to go along with observations about the ages of these trees. These mature trees show other hallmarks of their age, with low stem taper, crowns with thick twisting limbs, and lower trunk bark balding. Mixed among these are non-native trees such as Norway maple (Acer platanoides), sweet cherry (Prunus avium), and crabapple (Malus). The understory is a combination of native and non-native shrubs, including spicebush (Lindera benzoin), common witchhazel (Hamamelis virginiana), occasional American hazelnut (Corylus americana), plus a rogue’s gallery of Asian viburnums (Viburnum sieboldii, V. plicatum), Japanese holly (Ilex crenata), Oriental photinia (Photinia villosa), and Japanese aralia (Aralia elata).
Parsing these remnants over the years has allowed me to understand the watershed’s history
Among the houses within the Carpenter’s Run watershed, numerous remnant oaks and tulip trees infiltrate the front and back yards; in some cases, a lone tree occurs in an odd location in a front yard, or far too close to a house to have been intentional. I have often wondered how these trees survived house construction before reminding myself that the trees were half their age during construction, and thank the foresighted builders who preserved them. When envisioned from above, what emerges is a dense canopy of mature forest in Carpenter’s Woods with strands of pre-suburban trees filtering through the surrounding neighborhood.
Turning left from our front steps reveals a much different story, where the neighborhood is fully developed and the clues to its botanical history and limnology are less obvious but equally rewarding. This part of my neighborhood lies in the Monoshone Creek watershed, a stream that forms a broad valley and encompasses much of our West Mount Airy neighborhood. The Monoshone itself runs in culverts under Lincoln Drive, though few visitors will realize it while careening along this drive, which was built as part of the city beautiful movement in the early twentieth century. As a result, the mature trees that populate the Monoshone drainage are less obvious, but parsing these remnants over the years has allowed me to understand the watershed’s history.
In the few blocks directly across from our house, massive white and black oaks are peppered among the 1920s houses of the neighborhood. These oaks are similarly an extension of Carpenter’s Woods, and provide habitat for many bird species that we watch from our front porch, with my favorites being the variety of woodpeckers, including regular visits by pileated woodpeckers. Strangely, during the depths of the pandemic lockdown, a lone wild turkey ended up perching in the oak across from our house, a sight never seen before or since. And as common as they are, I am astonished by the squirrel dreys, the ultimate tree houses, often scores of feet in the canopies. In mast years we fall asleep to the drum-beat of acorns bouncing off of car roofs, and walking to our car is like being in a sea of marbles, reminding me of a slapstick comedy. People ask me what can be done with this ocean of acorns, which form a thick flour in the street when crushed by cars, and I often think of a cottage industry of Mount Airy prosciutto, raised on local beech and oak.
A walk along Wayne Ave, a former trolley (and current bus) route, which makes its way from Lincoln Drive up to the edge of Carpenter’s Woods, traverses the full height of the Monoshone catchment. The mix of houses along this road are typical of the neighborhood, but walking downwards from the crest of the hill, a scattering of mature trees are remnants of the larger forests that must have once covered this area. Mature red oaks, white oaks, and black oaks, along with massive tulip trees, grow among a mix of large single-family and smaller semi-detached houses. At certain points you can catch glimpses across the Monoshone Valley and see a similar mix of mature trees on the crest of the opposite hillside.
Untamed fragments of the Monoshone Creek appear occasionally as free-running tributaries, serving as reminders of how this landscape appeared before the spread of commuter railroads and houses filled the landscape. In one case, a few aging specimen trees around a large multistory apartment building indicate the grounds of a former estate. A small stream runs through the property before being consumed by a mass of bamboo and then disappearing under the street. Similarly, at the Germantown Unitarian Church, where mature white oaks and tulip trees dot the top of a hill and its slopes, a narrow tributary appears through a remnant woodland and then is subsumed beneath Lincoln Drive.
In mast years we fall asleep to the drum-beat of acorns bouncing off of car roofs, and walking to our car is like being in a sea of marbles.
Numerous houses line Lincoln Drive, in the floodplain as it were, and their rear-neighboring houses sit at least a full story higher, being built on a sharp bank above the Monoshone. From the ground floor of these higher houses, it seems that you can see directly into the second floor of their neighbors, an odd artifact of the local geography. It is along one of these sharp banks that a grove of mature blackgums is interspersed among several houses. On a recent late summer morning I happened to walk by as a blush of robins was making their annual feast on their fruits.
As Willie Nelson sings in “Yesterday’s Wine,” “miracles occur in the strangest of places”—I think of this line whenever I see the massive, ram-rod tulip trees and American beeches that occur in odd locations, close to houses and in backyards. Again, I can only surmise that these trees pre-date the houses that they shade, and were kept while the neighborhoods were developed.
At one of these houses along Lincoln Drive, a colossal sycamore grows mostly obscured in the backyard. This tree is far out of proportion for the space it occupies and grows on what appears to have once been the streambank of the Monoshone Creek. In the side yard of a nearby house are a grouping of four large, single-stemmed sycamores, growing in an oddly rhombic pattern. I can see no reason why anyone would have planted this pattern intentionally and can only surmise that they are old basal sprouts from another large sycamore that once grew along the Monoshone. Away from these “creekside” sycamores, on opposing sides of the stream valley, are two sentinel white oaks, their positions marking what was once the transition from floodplain to upland. These two oaks, growing nonchalantly in the side and front yards of their respective houses, have witnessed the transition from forest to rural landscape to suburban development.
Having lived in this neighborhood for nearly 25 years, my deeper understanding of its botanical history began to clarify during the Covid shutdown, which allowed me the luxury to study my neighborhood more closely. Having the time for long walks and contemplation revealed previously unseen patterns and provided a welcome lesson in the value of observation leading to revelation.
Anthony S. Aiello is the associate director for conservation, plant breeding, and collections at Longwood Gardens in Chester County, Pennsylvania.