American holly (Ilex opaca) is commonly planted in Philadelphia, and it has naturalized quite well here too, as a walk along the Wissahickon will clearly indicate, especially in the wintertime when this plant’s coriaceous and spiny leaves show green through the woods of the Wissahickon, and its red berries are usually the brightest color you can see among the subtle tones this time of year.
This is a pretty nice looking plant, as one can see in this illustration from Francois André Michaux’s “North America Sylva”, from two centuries ago:
And so one can see why it is so popular to plant now, and why it has been since John Bartram‘s time (this is one of the plants he shipped over to England, in the earlier part of the 18th century, when North American plants were still so new to European gardens).
For years, I’d thought that the American holly was native to Philadelphia, however, while it is most certainly native to eastern North America, as Joel Fry pointed out to me a few years ago, it quite likely was not growing in Philadelphia prior to European colonization or quite some time into that era, for that matter – similar to the case for the eastern white pine (Pinus strobus).
In William P. C. Barton’s 1818 Compendium Florae Philadelphicae he writes of the American holly: “A beautiful evergreen tree, bearing scarlet berries. In Jersey, near Haddonfield. Rare.” Also, it is it not listed for Philadelphia in Ida Keller and Stewardson Brown’s 1905 Handbook of the Flora of Philadephia and Vicinity – though it is listed for elsewhere in Pennsylvania, and in New Jersey and Delaware. It also doesn’t appear to be in Peter Kalm’s Travels into North America, which document his visit to the new world, including Philadelphia, in the late 1740s. Nor is it listed for Philadelphia in Thomas C. Porter’s 1903 Flora of Pennsylvania (he does have it for Bucks, Delaware, Chester, Lancaster, York and Dauphin counties, though). It is, however, listed in Edgar Wherry’s 1969 Check-List of the Flora of Philadelphia County, Pennsylvania, and so we know that by then it had established itself here. Also, in the herbarium of the Department of Botany at the Academy of Natural Sciences, there is a collection that arrived via the Wm Wynne Wister herbarium in 1899, that says on its label “Wissahickon – Wister” with a date of “Jun 7, 1863”; and so that might be its earliest recorded date – however, because Keller and Brown (1905) don’t have I. opaca as being in Philadelphia, and this collection precedes their work, that would leave that assessment a bit open to question; also I. opaca is not listed in Fogg’s Annotated Checklist of the Plants of the Wissahickon Valley (1996). Additionally, there are not any entries for Ilex opaca for Philadelphia in the NYBG virtual herbarium. Also, in the library of the Academy of Natural Sciences, there is an annotated copy of “Gray’s Manual” [call number: QK183 S644] in which plants that are “found within 15 miles of Broad and Market Streets, Phila., and in the herbarium of C. E. S. [=Charles Eastwick Smith]” are noted (by the aforementioned C. E. Smith), as having been “found in 1860-68” – and Ilex opaca is checked. This could mean it was found elsewhere in Pennsylvania, and does not necessarily indicate that this species was in Philadelphia, though.
Given that this plant is quite showy, especially in the wintertime, and also given that John Bartram, and others later on, were selling it, thereby providing an economic impetus for finding sites where it grew, it seems as though if it had been here, that those earlier botanists would have known of it and noted it, and for the latter, they quite clearly did not, thereby making the former quite likely, and its absence from early Philadelphia quite likely as well.